What do we know right now about the next "Grand Theft Auto" game?

I love games, but I don’t really keep up with the industry gossip and press releases and interviews and all of that. I find that it just makes waiting for games to come out even harder, so I’d rather not be counting the days until the next entry of my favorite franchise if I can help it.

On the other hand, the “Grand Theft Auto” series has proven to be a visionary and engaging franchise that’s really pioneered the “sandbox” approach to console games - that is, games that create an engaging, immersive, interactive world and then let you run wild in it.

Other than that it’ll be on the PS3/Xbox360, what do we conclusively know about the next installment in the GTA series? What has Rockstar said or confirmed about it in interviews? Even if there’s not much that’s been released or confirmed yet, what are the probable or believable rumors?