Marioface5: As for the idea that "every small-to-medium release" could "go Steam only", I don't think that would ever be a concern. Like I said, this is only an issue for a tiny handful of games here, so clearly this is no problem for the vast majority of developers.
Kardwill: Yeah, but the "tiny handful" are the games that tried to get here, and didn't succeed. Many other tried, succeeded, and got enough money on GOG to keep doing business here.
If they don't have the possibility to "pull back", many of those successful devs wouldn't have taken the financial risk, and those games wouldn't be there either. So the impact would be far greater that this handful of games and devs.
Keep in mind that these failures are games that the dev AND GOG thought would make some good business here, like any other.
Is there really much of a financial risk though? I get the impression that it doesn't cost much to keep the GOG version of a game properly supported, especially because again there's not even 10 games that I know of where it's an issue. Let's look at the games I do know of, and maybe that will give us a clearer picture:
1. Slender: The Arrival - This game, according to GOG users, is over a year out of date and is missing free DLC on here. There is no paid DLC for the game, just free updates which aren't here.
2. Luftrausers - This game apparently can't be completed due to a bug that the game had on release. The Steam version was fixed just days after release, but the GOG version wasn't. No paid DLC involved, just one free update to fix a major bug.
3. Sam & Max Save the World - This game has a near game-breaking bug that the developer won't give GOG a patch for despite having the bug fixed elsewhere. Again, no DLC, just a free update to fix a major bug.
4. Hammerwatch - This game is missing its latest update, though I'm not sure why since until then it was properly supported. It's missing one free update, no DLC involved, and that free update makes some nice gameplay improvements. Additionally, because of the version difference it is currently impossible for GOG and Steam users to play online together.
5. The Escapists - The DLC is out on Steam but not here. However, it is confirmed that we will be getting it.
6. Hand of Fate - The DLC is out on Steam but not here. However, it is confirmed that we will be getting it.
Notice anything weird about these six games? Four are missing free updates with no DLC involved. Updates that should cost little, if anything, to get to GOG. Meanwhile, the two games that are missing DLC are now confirmed to be releasing it here in the future. I don't think this has anything to do with financial issues or financial risk. I think these examples make it clear that it's just about whether or not the developers care about their GOG customers. They could update their games if they wanted to, but they don't care, so those games are abandoned. Developers who are okay with abandoning their GOG users don't deserve to sell their games here.