I'm afraid you're likely to get a lot (more) of aggression because of this post. It's mostly down to a lot of people on this site disliking steam, together with a poor choice of words with the term "Merger".
What you're suggesting is some kind of partnership between GOG and steam where they will recognise each others sales, and provide corresponding keys. It won't work.
This is partly because financially this would be a nightmare to identify who to credit with the sale, did they buy the game for the steam key, or the GOG key? The only solution would be a total split of those sales, which would severely cost Steam, as they are the bigger fish.
The bigger issue here is our old friend DRM. Steam likes DRM, they like you being plugged into their app, and they like having you there to fire adverts at, to seduce with promotions, and perhaps to track your habits (unverified). There's no reason they'd open up their platform to a less restrictive service that would just encourage users to not endure that stuff.
Overall, you're hopefully not suggesting a stockmarket style merger between the two companies, just a partnership. That won't happen.
