It's true. The Mars Volta have been playing shows with new drummer Dave Elitch for several months now - I saw them myself about a week ago. I was pretty bummed out when I heard the news because I was a great fan of Pridgen and his playing but I will admit that Elitch impressed me. His take on their older material was much closer to the way Jon Theodore played it and he was overall just extremely solid.
Theres an interview with their new drummer at http://www.mikedolbear.com/story.asp?StoryID=2120