... is there any chance of more of them coming to GOG?

I would especially like the Level 9 ones.

I can't imagine the lack of ScummVM support was the reason they weren't here.

ScummVM support is nice (and surprising as at one point they said they will never support those), but I don't think ScummVM support has anything to do with those games being in GOG catalogue.

There really isn't any technical issues that would have prevented selling them before, most of them, possibly all of them can be played in DOSbox and similar applications, so there are two major problems:
1) the IP right situation can be very complicated
2) there are very few people who would buy text adventures, so spending any resources to clear legal things isn't worth anyone's time really.

I would be happy to see those games here, but it won't be happening realistically.

GOG has sold https://www.gog.com/game/the_zork_anthology for years, but it doesn't seem to have paved the way for any other Infocom text adventures.