Yeah I agree that they "could" screw it up badly, G/S/C are my favorite of the pokemon games. If they do make a remake of them then I hope no changes are made to the storyline or which pokemon are in there. The remakes of R/B/Y were pretty good, and Nintendo is known for making the funnest, most original games around. So I think they'd turn it into something good and worth buying.
I think that if they would make a remake of it, then there would be a version for DS and for GBA, kind of what they did with Blue Rescue Team and Red Rescue Team. It wouldn't matter to me since I just play on my emulators instead of my DS now.