That would be my guess too. I was kind of thinking with Deadly at least, it would be nice if Jerry could dub his voice since (a) it would give Jerry a chance to take part in some way in The Big Relaunch Project and (b) UD is one character whose voice is such a big part of the character - the longtime Shakespearean ham actor! But cool as that may be, that still opens up the "Walter syndrome"; if he was voiced by someone other than a currently active Muppeteer, it would limit the character's ability to do live interviews for the movie's promotional media blitz and beyond, Deadly may come into a bit more prominenance.