To repeat myself from old threads, it would be awesome to have something like a WindowsBOX, like DOSBox but emulating (probably) Windows 98SE, fully open source. GOG could use that for old Windows games and never have to modify the games themselves. I would be happy to support GOG developing an emulator like that, rather than making old games run on new Windows.
The things GOG is improving are some bugs that occur mostly in games, e.g. something with color palettes in pre-2002 games. But I think every game using DirectX 9 or later will work without any adaptations, even ten years from now.
That said, there's also something to be said that if a game is patchable, there is some value in patching it to run directly rather than "need" an emulator.