According to information from a Q&A session last month with Rockstar North, it seems that GTA V will be set in a different universe from previous GTA games, except for GTA 4.
The information came when answering a question about the referencing of characters across GTA III and GTA IV, the developer replied:
“El Burro is referenced as he was also referenced in GTA 1, so it felt appropriate that he should cross “universes” – the “universes” are the worlds interpreted at different definitions, 2d, 3d and high definition, so we felt brands and radio / back ground characters would exist in both, but 3 dimensional characters would not.”
“This is the logic (as far as it could be considered logical) behind it – so no, we don’t believe any GTA3 characters could exist in the GTA4 universe.”
This means that GTA III characters couldn’t exist in GTA IV (which they didn’t), and thus other GTA characters from the GTA III generation of games wont be making an appearance in GTA V but we could see characters from GTA IV show up, however this isn’t confirmed.
This means that those who thought they spotted old characters throughout the GTA V trailer will be sorely disappointed to find out that CJ and Tommy wont be making a re-appearance.