Yes, Rockstar is coming out with a 'GTA 5.' It will be called Grand Theft Auto: San Andreas. You can go to this site for more information, but as far as I know, they're only releasing it for PS2 this time. But that's what they said about GTA3 and Vice City, isn't it? I guess we'll have to wait and see if they hold out on their word this time.
If you are talking about the mod to make Vice City Multiplayer capable, I believe you can go here.