There's something I was just thinking about recently. In recent movies and specials, as well as The Muppet Show Comic Book, we pretty much get all of the core Muppets - Kermit, Miss Piggy, Fozzie, Gonzo, Rizzo, Pepe, Bunsen, Beaker, Rowlf, Scooter, Statler, Waldorf, Dr. Teeth, Floyd, Animal, Janice, Zoot, Sam the Eagle, and The Swedish Chef (and maybe Walter, Bobo, Link, Sweetums, Robin, Lew Zealand, Beauregard, Crazy Harry, and The Newsman... In fact Pepe and Rizzo might have to be grouped under these "maybes" when it comes to recent productions).... But on The Muppet Show, we didn't get every "core" character in every episode. Many of these might be more "core" now than they were during the TMS era, but even then, if you limit the core cast to just Kermit, Piggy, Fozzie, Gonzo, and Scooter, it was fairly common for at least one of these characters (okay, never Kermit) to be absent (though it was the least common with Scooter, considering he was at the start of every episode for three seasons).
You can also say this about MuppeTelevision and Muppets Tonight. I'd consider the core cast of MuppeTelevision to be Kermit, Digit, Gonzo, Leon, Bean, Vicki, and maybe Clifford, Lindbergh, Waldo, and Link. So of these characters, Waldo was seen the least, and most of the others were in nearly every episode... But Clifford was absent from First Show and the Dog City pre-show (that one seemed to have the least amount of recurring characters of all the MuppeTelevision episodes), as well as non-behind-the-scenes footage from Secrets of the Muppets (if you count that). The pre-show for Dog City was also the only one to not include appearances by Gonzo, Leon, or Link Hogthrob. Besides that pre-show, I think Lindbergh was absent from Garbage and Food.
With Muppets Tonight, I consider the core cast to consist of Clifford, Kermit, Gonzo, Rizzo, Johnny Fiama, Sal, Seymour, Pepe, Bobo, Bunsen, Beaker, Andy, Randy, and maybe Nigel, maybe Statler and Waldorf (well, those three were in every episode). But most of these characters were absent from at least one episode. If you count the clips from past episodes featured in Best of Muppets Tonight, then I think Clifford, Rizzo, Statler, Waldorf, and Nigel are the only characters who were in every episode (and if you don't, then only Rizzo, Statler, and Waldorf were). Gonzo was absent from the Billy Crystal episode (and only appeared briefly at the end of the Cindy Crawford one... I kind of feel like there are more he was absent from). Kermit didn't appear in Johnny Fiama Leaves Home. It took awhile before Seymour and Pepe started showing up a lot (though in production order they had a scene in the second episode, broadcast order-wise Seymour was first seen in the third episode, Pepe first glimpsed in the fifth episode, and their first major appearance being the first episode after the hiatus between the sixth and seventh episodes). I'm thinking that the second season had episodes without Andy and Randy, but I can't think of what episodes off-hand (unless you don't count the clips in Best of Muppets Tonight). Bunsen and Beaker didn't appear between episodes 1 and 6, but after that they appeared a lot more for most of the shows run, though they were absent from Johnny Fiama Leaves Home and Best of Muppets Tonight.
Anyway, back to this series, I wonder if it will be common to see certain main characters absent, like in the older shows. I don't really expect there to be episodes without Kermit, Piggy, Fozzie, or Gonzo, but I could see there being episodes without the whole Electric Mayhem (maybe even episodes without Animal), Bunsen and Beaker, Rowlf, Pepe, and so on. But I could be wrong.