A GTA being announced sounds like a possibility, not sure if it'll be "GTA 5" though.
As for my favorite, I've actually got the same as scottie. Not sure if it's for the same reasons, though. All I know is, GTA 1/2 multiplayer on the PC was awesome.
I'd agree with others on a HD+Wii multiplat being unlikely. Wii games that are simply watered down HD games (which is what GTA V would be) don't do all that well.