I'll be really excited about Fallout 4 when it comes to GOG, but until then I'm just leaving it on my wishlist for a future reminder. Now that Bethesda is on GOG the footwork is present for seeing more of their games here in the future, and now that GOG has Galaxy, some of the optional modern game client features that such a company would like to have available in their games to have feature parity across distribution platforms are now viable going forward. Galaxy being early beta probably means we wont see big name AAA titles like that come here immediately, but at least some of the groundwork is laid down.
The game will probably pound my system equal or more than Witcher 3, so I'd rather wait it out and hope for a GOG release in 6/12/18/24/500/1000 months or whatever it takes.
Also, I love Bethesda's games but they usually stop patching them and leave them with literally thousands of game breaking bugs *cough* Skyrim *cough* so as much as I love their games I'm not eager to shell out $90 or whatever for a new release that might not ever get patched enough to be stable and reliable knowing that eventually the game will be $10 or less on a 75%+ off seasonal sale somewhere sometime in the future... hopefully on GOG.com. That gives me time too to monitor gamer reviews and feedback, and see if there is any need for the gaming community to make a big monga huge patch to fix bugs in the game that the company doesn't fix.... like Skyrim's unofficial patch that fixes about 234892347234 bugs. :)
Still... love your games Bethesda, your buggy games. :) Make one super stable and reliable and patch the hell out of any widely reported bugs ongoing until they're all fixed though and I'd be happy to shell out day 1 price for a hot new stable supported game.