Probably not, but this screenshot made an appearance on the net today. Leaked screens are very rare, but take a look and decide for yourself. I have attached a larger version in the image section below. Now if this is old I apologize as I have never seen it before myself.
Update: Rockstar says that the screenshot, is a hoax.
if it is, then it looks like a very early version.
I really can't tell. When it comes to the information bar, It seems to look like GTA. But unless the next GTA is going to have a female as the main character and by the looks of the vehicles, be in the 50's. I see this as being bogus.
I think it is a fake but kinda cool.
If it is real then the lead character is a woman and it looks like it is set in Cuba or Miami! maybe it is just a screen of GTA vice city stories for the PSP!
Is she carrying a mace? GTA4 better look a lot better than that... and who uses a spiked ball on a chain anymore? Gladiators? Knights?