Writer/director David Twohy is definitely returning to the land of Riddick, but based on this early report from Moviehole, the series seems to be heading back to the low-key Pitch Black approach and not the ridiculously over-produced tone found in the sequel, The Chronicles of Riddick. Yes, Vin Diesel is back.
Apparently casting is well underway for the as-yet-untitled Riddick 3, but those guys at Moviehole have read the script and if you don't mind a few minor spoilers, you can see what kind of characters the production is casting for. As for the plot, it seems to be a throwback to the first flick: Riddick stuck on a planet with unpleasant people and even nastier creatures. Insert mayhem here.
One interesting note found in this piece is the assertion that Riddick seems to have found a sense of humor. I'm not sure if this is good news or bad, but any time you combine action and sci-fi with monsters ... I'm interested. Yes, still interested even after the goofball experience that was The Chronicles of Riddick.