I hate to predict they are killed...
Claude - After being wanted by the whole LC, escapes town and maybe back to San Fierro.
Tommy Vercetti - Lives his great life as the drug baron and gets kids but he retires etc...
Carl Johnson - Wiped out the Ballas and Vagos both. Best life he can have, so safe as hell.
Lance Vance - Survives Tommy's bullets and escapes by the Maverick parked on the roof.
Vic Vance - He didn't die in VC intro, no where did his name get dropped and as we know Lance has another brother (Pete).
Toni Cipriani - He doesn't do crimes anymore, just a fat slob sitting with his mother at home.
Donald Love - Either escaped or kidnapped by the Cartel, but I doubt that he was kidnapped because then Catalina would act brave and send you to get him with leaving some money, like Maria.