Sony has begun making their games require PSN account. Will this happen here on gog, or will the game be pulled from the store?

So far, PSN account requirement hasn't been retroactively added to their older games. Also, GOG's DRM-Free policy means each game needs to be playable offline in single-player mode without additional software or accounts. Online multiplayer might be another story.

In this case, Sony have three choices.
1. Release their newer games after some time, like 2-4 years after DRM-ed releases (in this case, GOG version of Ragnarok won't require a PSN account).
2. Do not release any new games, but keep the current ones (The story of Kratos and Atreus will remain unfinished).
3. Request removal of all their games (same as above, but current owners will keep the first part of the story).

PSN account should be an option. I would love to use it.