I wouldn't say so :/ I mean, it'd be great to see, but I think they're probably more concentrated on making new games. Besides, the others are right -- we can fill up the Pokedex. Without FR/LG, you couldn't before (not without cheats). When it came out, you pretty much could.
Would I want one? Yes =3 GSC was awesome. I had a fun time playing it. I just wish they would. ;_;
Oh, and I think Celebi can be obtained with a Japanese bonus disk for Colosseum...