How many releases of GTA are we supposed to expect?

I haven't heard anything about the next GTA yet, I'd kinda like to see a GTA Western though, that'd be kool to car jack horses and wagons. Grand Theft Auto: Ol West coming soon, haha.

Yeah, space ships would be cool! It would be Freelancer, with the ability to roam free... and rolling out onto planets would be cool. Of course you'd be able to survive a drop from the moon to Liberty, long as you had full health to start with.

Maybe a GTA MMOG? On second thought, that just might be too chaotic for words.