The current Unity games are not affected by it, as long as not updated. However, all the Unity games i own (Edge of Eternity, Pathfinder Wrath of the..., and Pillars of Eternity, along with a bunch more) are already in a later stage of the game and basically fully mature. Not sure i will get new Unity games as long as i do not know what it means for me as a "end user". Surely i have no intention allowing them to spy on my PC... although a lot of games are somewhat "spyware"... not new at all. The majority is okay, still.

As no-one has yet done so, a link to Positech's blog on the Unity situation provides some interesting details from a developer perspective (responsible for the Democracy series, Gratuitous Space/Tank Battles, Redshirt and Big Pharma).

Positech.co.uk: A longer perspective on the unity pricing fiasco

And now for loads of gratuitous follow-ups... ;)
Well, how about the fact that the Steam Agreement is actually titled a "Subscriber Agreement"? That flags up the likelihood of regular payments from the get-go. Of course there is no "need" for it - but with over 120 million users, imposing a (say) $5/month fee would bring in an extra $5.4 billion per year assuming a 75% takeup (and that's likely an underestimate given that those rejecting it could lose access to their games collection). Even if Gabe was "saintly" enough to turn that sort of money down, he's not going to be running Valve forever - and just as Unity's change of policy seems to have been driven by an out-of-touch management, the same could happen for Valve or any other company.
I think you've kind of answered your own question here.
See here for a counter-example. Yes, it involves iTunes - but it shows that purchased virtual content can be withdrawn and has been going on for several years and has now resulted in class action lawsuits:

9to5mac.com: Another class action lawsuit over the risk of iTunes purchased content removal
TheVerge.com: Apple lawsuit over "buy" and "rent" labels for digital content can continue, rules federal judge

This class action seems to have been largely dismissed due to lack of information provided by the plaintiffs. Unless someone can point to a result showing otherwise, this would seem to indicate (within the United States at least) that paid-for content can be withdrawn as long as the store/distributor mentions this possibility.

Compression is a trade-off between CPU and disk/SSD storage. Since most systems have storage capabilities in the terabyte range, why bother with compression if that results in noticeably higher CPU usage?

Now I would agree that Unity3D is hideously inefficient, in the unreasonably high demands it puts on GPUs to render relatively straightforward graphics (like the fixed perspective used in Pillars of Eternity). But I don't think measuring the compressibility of Unity data is a good way to quantify that.
Dreamfall Chapters, Wasteland 2, Torment: Tides of Numenera - none of these require online connectivity though.

They don't. But if a online connection is available, the RE will phone home.

hope this will result in much fewer garbage games
anything cant pump out the cost of this is not worth to be made

For sure. Hosting isn't free, and there is no way a company could be mandated to host some piece entertainment and offer downloads for all eternity.

A distribution model where in exchange for payment, I grant access to a download for (say) 30 days is entirely legit.

I'd still think it would, however, be legally risky e.g. for GOG to start randomly pulling games from users' accounts for no reason other than the publisher wanting to cut costs. After a quick skim through the agreement, I don't think their black-on-white really reserves the right to pull content for reasons other than breach of terms or the need to stop the services permanently, but I also don't think they exactly promise to make things available on permanent basis. In vague cases like this, I would expect European judges to side with the customer, especially if there is years of precedent suggesting that sales are permanent. (I'll also note that GOG's agreement never uses the word rent, lease, or subscribe -- the relevant verbs used by GOG are 'purchase' and 'buy)

At the very least, I'd expect them to change the agreement first.

Not every system has Terabytes of storage. Even if they do, that eventually gets filled up. I just added my 5th drive to my NAS raising from 27TB to 37TB storage, while my gaming rig only has 2TB space.

But regardless, it's an OCD thing i have. I've been taking manga i have and recompressing (usually 6Gb results in 500Mb saved), Not only that i only have a handful of games extracted at a time, why waste the space? I'd rather optimize. The type of games and the type of media determines the steps i do, from ECM then 7zipping down ps1 games, to recompressing images, to finding duplicates and leaving a restoration batch file to restore the duplicate files. In some cases i've found a zip inside a game folder that contained... the entire game... Meaning i saved half the space by removing an accidental inclusion of unneeded data.

I was just saying a number of unity games tend to take up a lot more space than they need to. Games with a lot of assets tend not to have the huge 20:1 or 50:1 compression ratio you can get. While games with few added assets tend to be bloated in size. As for how this affects performance, i wasn't talking performance specifically.

In some cases, compression can actually improve performance. Consider that:
* Compressed files take less time to load from disk into memory.
* There exist fast (de)compression algorithms, like LZO (and I think LZ4), that take very little CPU. They're not as effective as more popular algorithms, but using one minimizes the CPU usage while still getting some benefit from compression.
* Also, there's texture compression, which GPUs support. (Though there's a lack of standardization here; mobile platforms use different compression algorithms than desktop platforms.)

The removal of bought digital content isn't really new.
I agree.

GOG has already pulled content from users' libraries. I know of at least two occasions.

Using a Content Delivery Network (CDN) makes bandwidth costs negligible (see this Backblaze blog entry for some cost examples, like Amazon Web Services starting at $0.085/GB). Even if you only purchased content at a 80-90% discount, you'd have to do a lot of downloading to come anywhere near the cost of the game in question.
Agreed - GOG's record here has been impeccable so far with delisted games still being available to their purchasers. However the discussion was about Unity's ability to effectively "revoke ownership" and the iTunes example does provide a good indicator that they could do this. Plus it's another example of Apple's control freakery (Disclosure: I own no Apple products aside from a 1982 Apple ][ Plus plus accessories).
Rather than doing things the hard way, why not just try using NTFS compression on the games in question? Or if you really want to give things a squeeze, check out Pismo File Mount which lets you treat ZIP archives as folders - so games in such folders have data automatically compressed/expanded as needed.
Agreed, but typically when you have a fast CPU and slow storage (so the time saved on reading/writing less data outweighs the compression overhead). With most gaming systems using SSD or NVMe, this is much less likely to be the case. Plus the largest files most people have tend to be either video (compressed with lossy algorithms) or program installers (almost always heavily compressed to reduce bandwidth costs).

What if I'm not using NTFS? (On Linux, NTFS isn't used much, and I wouldn't trust the driver to handle advanced features properly or even at all.)

Unity need to stop playing games and be more transparent about their pricing

It seems like this drama suddenly ends with Unity's damage control.

https://twitter.com/unity/status/1703547752205218265

"We have heard you. We apologize for the confusion and angst the runtime fee policy we announced on Tuesday caused. We are listening, talking to our team members, community, customers, and partners, and will be making changes to the policy. We will share an update in a couple of days. Thank you for your honest and critical feedback".

So they hope. I guess it depends on what the changes are. We will have to see.

Yeah, that's empty as my water bottle currently is, meaningless until action is taken.

Plus, they've poisoned the well and shown they're willing to go as far as they did without consideration prior.

I imagine legal threats started to file in.

It's worse than that - they've shown they can do this with a year's thought going into it, if we assume this was the plan when they started removing the parts of the ToS about electing to stay on an old version. Certainly 5 months' planning, for putting April 2023's changes into place.