That still remains the latest release from Rockstar. There's no news on any upcoming GTA titles, although I'm 100% sure there will be more from the stable.
In the meanwhile, you might want to try Mafia 2 if you haven't already done so. It's the same gameplay, better story IMO. Another one is L.A.Noire. It's already out on the consloes, will be out on PC in November.
Mafia 2 is similar to the GTA series, but it lacks free roaming a little bit.
As said, GTA's episodes from liberty city is the latest one yet. Rumors are there about a newly releasing GTA V, but it's yet to be confirmed.