Let me spend my two cents:
1. physical discs for PC will delay the release date.
Not only it take time for production, package, shipping to many countries, longer/more expensive customs service (for some counties) and so on. Most important that map and stickers they can print about today and have their months for logistics 'till release. But discs need to have most stable version. This is way too bad (as I seen on PS4) when inserting the disc you see something like "26GB update required", you know.
So the question is: does it worth to get game disc in ~August 2019, or the very same game in April? =]
Still there is no DRM so you always can burn your own (or to order from others) disc to put in genuine case =]
2. As CDPR release their games on many distribution platforms but push forward the DRM Free conception, it's logical that discs/codes might be for GOG. And the one of great GOG functions is to support user's freedom to choose game version they want (e.g. I may not like some update/patch of game I paid for. In Steam I have to update even if I don't want to. GOG doesn't force me, at least in case of single player games)
In this point of view preassigned version on disc seems not quite well.
As for me, I think that physical distribution had to migrate to flash drives a long time ago. It's not too expensive to produce unique packaging USB drives (I ordered 50 pcs USB 3.0 32GB drives with custom logo from China for ~$3 per piece. This is far from wholesale amounts, so I believe that even really unique casing drives with good reading speed in orders of tens of thousands pieces will cost not more than ~$2 per piece,)
disporting: I wish there was a physical release with disc. I imagine the game size would put me over my data cap, and take 2-3 weeks with my internet speed. I wish we had affordable unlimited bandwidth Internet where I live. :(
That's the matter I'm confused about all those "all digital console" and "Google Stadia" conceptions. Looks like those services is might be good in Russia and China, but US/AU/EU it's very questionable.
(well, right now I'm in Scandinavia. I can say they have a very good Internet as for EU but many ISP talk about (or already use) bandwidth limitations. Most expensive package is 100GB and its cost per month is more than any AAA game)
Still as GOG version is totally DRM Free I believe you'll able to get necessary files on BD/Flash drive very cheaply :)