Writer/director David Twohy has posted an update on his blog in which it sounds like plans for the third "Riddick" feature with Vin Diesel seem to be coming to a head. Here's a shortened excerpt:
"The hurdles seem to be dropping. The final turn is being rounded. The finish line (actually a starting line) seems closer than ever.
Of course, there are no guarantees in this mad endeavor called “filmmaking'… but we’ve reached a critical mass of enthusiasm and resource needed to launch a movie. If we go now, we can make it now. If we don’t, we may never. And trust me, we’re all keenly aware of that.
Vin will be the driving force behind this next movie; I’m merely the writer-director. Am I being facetious? Kinda. But kinda not, too: It’s Vin and the concessions he chooses to make that will allow this movie to go forward. And his love of the character, of course."