Or Disney could decide to keep The Muppets as a franchise for its more family-friendly Disney Infinity instead.
The Muppets should be in DI instead of KH for 2 reasons.
1...Hey! Kermit the frog and Animal toys!
2 is much more complicated.
You see, Kingdom Hearts is a Japanese video game series, and a very Japanese one at that. And while Disney movies and Mickey characters are hugely popular over there, The Muppets outside of Sesame Street (which is huge over there) aren't really a thing in Japan. Sure, they've dubbed the movies and maybe had one or two of the TV shows, but it's one of those cultural translation things. It's the equivalent of how these cheap little Pokemon/Yugioh knockoffs (Beyblade and the like) are popular (supposedly) with kids in the Western world when they're barely popular at that in their native country while long lasting, iconic mainstays like Anpanman, Tensai Bakabon, and Doraemon (which we only got a dub of
last year and it isn't exactly blazing trails) usually never get imported due to weird cultural bits that we don't get. It's also the reason why we didn't even get the Asterix animated movie
made specifically for the US market (pop culture gags, changed terminology, American voice actors they animated directly from). Some stuff just doesn't take. And unfortunately, the Muppets are one of them.
To drive the point home, you know what they picked for the next KH game? Big Hero 6, a film that, while it had a slow opening due to being released in that country opposite a
gigantic kids' franchise from their own country, managed to gain popularity in the long run. In other words, something they know about, heard of, and is popular enough to be exciting.