Sorry for being a negative Nancy but, isn't the 50th anniversary in two years away maybe one of the cast members that were recently let go could passed away in two years, so we should not get our hopes really high yet.
I am speculating here, but I would guess the 50th anniversary special - maybe not the season is already in the works. This is a huge milestone for any kind of program, let alone one as iconic as Sesame Street. I would bet, or at least hope, that they are filming interviews or inserts with all the principle players in front and behind the cameras now to be able to have as many veterans represented.
Fifty years is a lot to celebrate and cover in any one particular special. My fanciful wish is PBS would dedicate time on some of it's other programs to highlight aspects of Sesame Street that might fit in with the other show's scope. PBS News Hour could do a week of pieces on various aspects of the show. The American Experience could do an episode about the impact of Sesame Street on education and learning. NOVA could do an episode on Slimey in space (I am grasping at straws here I know), but I think there is an opportunity for PBS to have some synergy and really celebrate what they helped to create. (Yes, I know new episodes are on HBO, but PBS is the real home of Sesame).
Sorry, Muppetspot, I wandered away from your original post.