True. On the other hand, would there be a big audience waiting for the next Muppet movie without all of these tie-ins? Sometimes, especially if you know there might be some effort involved in packing the theater, it's better to explore other outlets for your property to increase awareness and broaden your base. The Hensons are just barely doing the "flooding the market" thing that Disney is doing. Yes, Red is popping up inexplicably at conventions ... but where is everyone else? Where is mention Dark Crystal? Yes, we have comics (for the above and Labyrinth), but that's about it. Is there NO ONE with vision at this company? At least the folks trying to get FR out are trying (still think Youtube Matt segments would be a great lead-in, particularly if him getting lost is the main plot of the movie ... we could see his adventures and then not hear from him ... BOOM ... we're ready to get him back in the movie).
I, too, tend to see a "Pixarverse". I don't know about Cars, as I've never seen it, but the bugs from A Bug's Life apparently live in the same neighborhood/city as the Toys, and Boo had Jessie, IIRC. Mr. Incredible was on a magazine IIRC in Nemo, but that's ambiguous about how real he was in that universe. He could just be a comic book character.
Not every movie needs a two, you're right. However, the ending to Labyrinth leaves us with a sense that it's not all wrapped up. The whole POINT of the movie is for her to put away childish things and the first thing she does when she gets back is get a party with fantasy friends? Jareth's reprise of Dance Magic also alludes to the possibility it's not over, as is the music video where we see "End" or something crossed out on a copy machine. It seems apparent this movie was thought to be something that could be exploited later, and we know from hearing stuff about Fraggle Rock how much Jim hated endings, but even with Fraggle Rock, it's not like they all die or anything. You could've made a sequel based in the Desert for all we knew, so I don't know why he griped about it so much. Heck, it's like Aughra says, "End -- begin." It's all the same if you think about it. The only ending I know of that basically shoves "THE END" down our throat is Dinosaurs. Everyone else gets some wiggle room.
it's so rare to see a sequel live up to the first, especially in the occasions (like this one) where a sequel is 10-20 years after the first one. Look at Son of the Mask. Was there any call for that to be made?
Is the new Tron out yet?
Secondly... and this is the snarky answer, Henson has enough problem getting Dark Crystal 2 and Fraggle Rock off the ground. The last thing they need is a third movie stuck in development purgatory.
It's not snarky. At least, not to me. It's a valid concern. However, what one does is keep everything on the table and then pick the one you're closest to making and do that first, and then do the others in succession when you can. The Hensons can't afford to get bogged down in projects. They need to devote themselves to at most two so that there can be some quality involved.