I've seen him do a lot of Sesame stuff in the new season. I think one time he started doing cookie monster during his letter segment, then switched to Super Grover and someone else did cookie. I think they switch on and off.
It kind of annoys me, not because i want Frank to retire, but because now I find myself trying to figure out who is doing which character. It's hard to tell sometimes. Eric's Bert is especially good. I'm sure if a theatircal release of a muppet move were done in the near future Frank would have some part in it, though I wouldn't want him to do voice over work unless it was for Sam and even that isn't needed because I thought Kevin did a good job on the voice and I'm sure could do the puppet work.
Anyway, I'm rambling, but before I end my rambling, i'll say this. Frank isn't officially retired and I'm pretty sure Eric is still considered an alternate for his characters, but Frank's voice for Piggy has started to sound a little too forced lately and so are some of the other voices. Also, his puppet work seems a bit off. the motion of the mouth doesn't sync up as good as it use to. I prefer Eric's rendition of his characters over Franks current performance due to age or even lack of interest.
Maybe I should have saved this little rant for someplace else.