Now that I think about it...
Muppet Movies really didn't make all that much in merchandise. Especially at the beginning. Other than soundtracks and kids books (the Marvel version of MTM counts as that). GMC had those collectible glasses and posters at McDonalds, but that's about it.
MCC had a regional fast food promotion... but MTI was probably the first to see anything major. Even then, a couple plush toys, a national fast food promotion, a CD-Rom, and some shaped bottles of bubble bath. MFS had different international Fast Food promotions... and I guess that was about it. A cancelled and unproduced playset... but nothing more than kids books. Even EIG had some things, plush, a sing along video, and a video game... FTB only had kid's books. I know KSY also had a kid's meal promotion (possibly regional, cuz the Dairy Queens I need an hour ride to get to don't serve hot food... well, one does hot dogs, but that's about it) The only other movie specific plush was the Nanco MOz plush.
We already have multiple kid's books and Pez confirmed. There's no doubt plush will be at the Disney store... and that will STILL be the most merchandise a Muppet movie ever saw. And I don't count retroactive stuff like Muppet Racemania (which used the movies as race tracks) and Palisades action figures.