I think that would be a marvelous idea, but for the simple fact that as each one that comes out, I and others must find it hard to go back to the predecessors before. IE... If this compilation were to come out, they would have to 'add' things to make GTA 3 and VC more enjoyable than the originals for PS2/Xbox, and updating the graphics isn't going to cut it, nor do I think Tropheys will..
Maybe if R* could pull off making a net for the game and having GTA 3, GTA VC, and GTA SA online modes similar to GTA IV. I know I for one would love to smoke friends in the Jet fights in SA.
In Conclusion, if they were to do this compilation and spend time, it could bring the 'GTA 3 Era' back up on the pedestel, and if that were the case, I'd hope Rockstar would consider the idea of finally creating the end to a trilogy, 'San Andreas Stories'.
Personally I feel Rockstar walked away from an 'Incomplete chapter' to the GTA 3 Era... and it still can be fixed.