Here's a quote I found on another forum, regarding previous GTA protagonists not making a return.
"I know a lot of people have been speculating about if Tommy Vercetti (and others) return in GTAV. There is next to no evidence to suggest this other than a slight resemblance based off half a face.
Here's an interview from September 2009.
This in reference to
this picture.
He doesn't rule out a return to the GTAIII canon but considering the interview mentions that most of the characters are dead and the wall of graffiti shows RIP messages for Tommy, CJ, Claude and Toni. This is pretty solid evidence to suggest that in the present day they are all dead.
As far as Tommy Vercetti specifically is concerned Ray Liotta has been confirmed to have not appeared in the trailer.
http://uk.ps3.ign.com/articles/121/1211384p1.html - As far as I'm concerned that's enough to rule him out.
As well as the fact that R* have never used the same main charcter twice in a GTA game and the evidence shown above leads me to believe that non of the old charcters will be returning, at least as a playable charcter.
If I'm being honest I'd love to play as them again but let's be realistic here. Apart from a slight resemblance to Vercetti there's nothing to suggest that he'd make a return. It's not in Rockstar's nature to do something like that.
And you could go as far as saying that GTAV is the start of another world and canon, much like GTAIV was to GTAIII. We got 5 games out of the GTAIII canon and 3 out of the GTAIV canon. Maybe they've moved on once again? Who knows?"