Well, the ultimate demise of some of our beloved GTA Heroes is evident.. seeing as a few easter eggs in Grand Theft Auto IV suggests so. So the real question is, how did they die?
Feel free to add in how you think they died, or how their career ended, so on and so forth.
Claude
First of all, Claude was a marked man by the Leone family (as you find out later on in the game where Salvatore believes he isn't to be trusted anymore), and seeing as in one mission Claude kills Salvatore, this only douses gasoline into the fire, leading me to believe Claude was eventually hunted down by the remnants of the Leone family.
Tommy Vercetti
A lot of people think Tommy Vercetti was also a marked man since he was very much wanted dead by a lot of mafias/gangs. But after playing Grand Theft Auto: San Andreas, a cut-scene says otherwise (at least thats what I think). You'll notice that in one cut-scene in Los Venturas, that Ken Rosbenburg (Tommy's Lawyer) is talking on the phone explaining how Tommy V had a cocaine addiction, and had fired Ken Rosbenburg (since he was working for the Leones now), and was losing a lot of money - leading me to believe he died from a drug over-dose. But a lot can be insinuated from that cut-scene. However, aside from his death - the cut-scene also suggests his reign of power over Vice City lasted from 1986 - 1992.
Lance
Well we all know what happens to Lance...
Victor Vance
His death is pretty evident, seeing as he gets killed in the opening Cut-Scene to Vice City, and if you suggest otherwise - throughout Vice City the only thing you hear coming out of Lance's mouth is, "Man, they killed ma brother!"
Toni Cipriani
It's hard to say what happened to Toni, but I have a few theories.. From the Liberty City Stories era - GTA III, he gained a considerable amount of weight, and most people suggest it's because he was always tormented about how skinny he was - and due to his insecurity he could have had a heart attack from eating to much/being unfit.. Which is kind of silly for the death of a GTA hero. He also could have had a hit set out on him from the Triads, or possibly the Sindacco, Forelli, and Sicillian mafias.. Since he did pretty much kill the respective leaders/top dogs of all five families/gangs in Liberty City Stories.
Donald Love
Probably the most asked about character in the entire series, and we still yet to know what the hell happened to Donald Love.. Some say he was kidnapped by the Triads, others say he left town after Claude retrieved his valuable box since it was dangerous for him to stay in town with it in his possession.
Carl "CJ" Johnson
It's hard to say what happened to him, I think he was taken out by the mafia - as he did steal from the Leone family in Las Venturas.