The one things us fans must always remember, the characters all depend on who can play them. Muppet projects, be they movies, tv shows, or something as simple as a viral video may have to be shot at the same time as SS in some cases, leading Eric, Steve, Matt and David (again, depending on the extent they want to use Scooter and or Janice) to be unavailable, and Martin, Leslie, Carol, Kevin, and Joey (among others) will have to fill out the bulk of the other characters.Join the club.
I LOVE Sesame Street and will continue to support it through thick and then, but come on, lets be real. Besides Elmo, Abby, Telly & any Joey Mazzarino performed character, everyone else has been completely shoven under the radar.
This is not a bash against the other performers. As Drtooth said, it all depends on availablity these days, since the new Muppet movie will take up time to work on SS for most.
Now, I completely forget, but what happened with Jim, Frank, Richard, and Jerry when The Muppet Show was filming? Did they film it off season of the Muppet Show, did they just film inserts during their down time... or did they do a few in Britain?
They could always shoot some inserts during their off time with the Muppets (though, I'd kind of think they want some rest first).... That's the one thing that bothers me about the new format. Less time for insert segments, especially if they want new segments to be recurring in every episode... which I find out of the question if we're shown the same Abby segment three times a season.