Don't hold your breath. Last I heard, the release that Rockstar is planning for that title is exclusive to the PS2.
However, both GTA3 and GTA: Vice City already have modifications avaliable -- including ones that add multiplayer support (though the modifications that facilitate multiplayer may be limited to Vice City). There may be third-party applications avaliable that aid in the creation of mods, as where there is smoke -- large modifications produced by many individuals -- there is often fire...
...Or one of those new
GeForce 6500s without the Dustbuster2 on...