In Grand Theft Auto IV enter the Broker Safehouse and look to the left (or go into the buildings around South Bohan and go up some stairs). There is a special easter egg that consists of graffitti writing. But you can see many names of past GTA protagonists from the 3D Universe. All of the protagonists (Claude, Toni Cipriani, Tommy Vercetti, Carl Johnson, and Victor Vance, except Mike) are shown to have died, as there is writing like "R.I.P Toni" in the graffitti. However, Rockstar confirmed this was just a "little joke to fans". Victor is the only character out of the 5 who had a canon death, as he is killed in GTA Vice City). Maybe the writing is just a sign showing the 3D Universe is over, and the protagonists will not return in future GTA games. Fortunatley, the protagonists may still be living in some parallel universe.