I've been saying for a good while now that a KH MMO would print money. There'd probably be legality hoops Square would have to jump through for the worlds used in UX, but if they can get it done? I'm telling you, this game would be incredible if done right.
As it stands, it is probably the most important title when it comes to this next saga, and it's a shame that it's only on mobile devices. Not to mention, the user base for it isn't as big as it once was. They've already got the assets for Daybreak Town and most of the cast due to Back Cover. Even if it's just an offline experience, it still needs to be done.
In fact, some of the newer worlds introduced in UX have World Themes, and I highly doubt that we're never going to hear them outside of UX. In fact, some of these themes are some of the best KH pieces to date. You can hear that there's been a lot of work put into the composition. That's why I think we'll get a console version of UX at some point. We ended up getting Back Cover, which explained nothing, and the only reason why that was made was because Square couldn't justify sending out DDD on PS4 by itself as its own purchase.
They have more teams at Square working on KH titles now. That has to mean that we'll be getting a LOT more KH content compared to what we used to get, and probably more frequently. If they wanted to give us UX-R as a title to tide us over for the next 3-4 years until KH4, that's more than acceptable. Other than the Kairi DDD-style game and Verum Rex, that's the title people want the most.