I'll be the first to admit i could care less about simply guessing/speculating on artwork-type stuff like which Muppet graces the cover, especially when the release is a ways down the line (though i find it pointless and boring, others do care hence the existence of the post, and i would never say that such a post shouldn't exist precisely because of that).
But what i would say would lend a thread like this more merit and legitimacy would be thoughts on what extras should be included. Throughout the discussion, we may find stuff a lot of us agree with should be "must-haves" that might otherwise go unthough-of/uncared-about by the people putting it together, and as a result of sentiments posted here, fans could contact Disney and express what they want to see and be proactive about making sure they're done "right" instead of everyone collectively moaning about it later on when the official announcement is made and find ourselves disappointed with what is/isn't included after no one can really change it!
Especially with a season by season box set, if something's not included/done right, it's unlikely there would be a second chance to correct it later with a re-release...whereas the movies tend to get several releases, "complete box sets" are far less likely to get a re-do (even though it's not impossible - it did happen with the "Starburst Editions" of Farscape).
I would kind of like to see the specials "The Muppets Go Hollywood" or "The Muppets Go to the Movies" either released on their own or as a dvd extra, but i think these specials would be more appropriate as an extra on a future re-release of "The Muppet Movie" and "Great Muppet Caper" which are the reason the specials existed...to promote those particular films.
I personally root for the things that are directly connected with the production of The Muppet Show and wouldn't really fit in elsewhere as per a chance for fans to see them - the promos should be a no-brainer given - at least some of them were included in season one, but only a handful and dropped in other sets. I think a complete reel of these promos should be included for all 120 episodes...You put 120 30 second promos together and that's an hour of Muppety goodness! (And even then, they actually recorded a 30 second and 10 second promo for each episode). The Muppet Show promos were special in that they were done by the actual production team and not a network just throwing together clips with an announcer voice saying "Watch (show name)"...they were great comedy bits often with Kermit and Fozzie or other occasional characters...these are great funny entertaining pieces of Muppet history that should be preserved in this perfect place to showcase them.
I also agree the original versions of the Juliet Prowse and Connie Stevens episodes should be included. I know they must exist somewhere...they were still accessable five years after the fact for Christopher Finch to write about them in "Of Muppets & Men" and they could always borrow Museum of TV & Radio's copy of Juliet Prowse if they can't find any other copy.
Muppet Morsels were left out of S2 & S3 because they were "hard to do", but they were well appreciated! Take less work out of presenting silly graphics and present "just the facts, ma'am" and that's less needless energy expended! Or if it's hard enough to do the "pop-up" style commentary, at least have the more traditional voice-over commentary! Even just having Important Muppet People Who Were There just laughing along and commenting on random stuff even if the facts are short is still worth the price of admission to me!
And "Of Muppets & Men" the documentary special also needs to be on #4 or #5. S5 would be the most logical choice since that's when the docu was produced, but if they put it out early on S4 so S5 has more room for something like a complete promo reel, i'd have no complaints whatsoever, i'd be bouncing off the walls!