The relevant quote, which you can read in full below, shows that Criterion hasn't forgotten about Burnout--but being the shepherds of Need For Speed: Most Wanted and Hot Pursuit for EA seems to be occupying most of there time.
Here's what Sullivan said:
"There's still a lot of stuff we want to do with driving," he says. " We will make another Burnout game at some point. Obviously, as we're working on Nfs we're thinking of really good ideas that aren't right for this series; there are ideas that we're going to explore with Burnout. And we wouldn't be making Nfs or Burnout games if we didn't think the driving genre had a long shelf life and that we could push the boundaries. There's a lot of new stuff in Most Wanted,