I agree there needs to be a HD Triple Pack released or something...they did a fantastic job on the Xbox versions for GTA III and Vice City so on the 360/PS3 it would look incredible and playing the games again for achievements/trophies would be brilliant!
Does seem a bit strange they haven't done this yet they've released them all on A) PS3 but as standard releases and B) released both GTA III and Vice City on iOS devices etc.
The next gen has just begun and the successor to the 360 is pretty much set for 2013 so unfortunetly I am having doubts that they may not ever release a HD trilogy for the 360/PS3
*sigh*