I've been wondering if Frank Oz was coming back. He hasn't been on the show since Jerry Nelson died, and most of his recent performances (outside of parodies) featured Jerry Nelson with him. Would the lack of Jerry Nelson (not to mention Kevin Clash, Fran Brill, and maybe Joey Mazzarino) make him reluctant to come back?
I've read a few times that Sesame Workshop doesn't use Oz much because he's too expensive (and they have been having financial problems), and Oz did say in an interview that he comes back once a year "for fun", but in a more recent interview he said that neither Sesame Workshop or Disney ask him back because they have good enough replacements for his characters but is willing to come back.
It seems like Frank Oz hasn't directed a movie in years. Maybe he's been busy developing scripts that didn't get made, or maybe he's left projects/been replaced. I know I saw an interview with him where he said that he wasn't desperate for money that he was willing to direct bad scripts. But it does seem like there's been plenty of time where they could have used him as a performer.