I don't know if Clifford can come back as Elmo seems to be a full time job, not to mention the other things Kevin Clash does for Sesame Street. With Eric taking on Sam now (making him the first Muppet performer to take on ALL of a past performers characters, at least with Muppet Show characters) he wouldn'th ave much to do other than Clifford and many back grounf characters, but of course that's all he really did on MT so maybe he could work on a new show.
Wow, I just made a point and then refuted it at the same time.