There is an online server where an internal “reliable” insider within the SE team has shared some information about ML, prior to the cancellation of this game. Recently, this SE source has shared this screenshot of an internal SE document showing the list of possible worlds. The insider clarifies that it is this list of worlds was the “initial” one during the early stages of Quattro development. Because the current development differs a lot from this list, he stresses that Disney has “demanded” that the IPs of those worlds have to pass WDC's quality values. In early SE and WDC meetings, the SE team provides a list of films they “would like” to include in the next KH project and Disney gives their “preliminary” go-ahead. In the following meetings, it is decided whether that world will be confirmed if the “scenario” design is suitable for Disney. So, there are quite a few worlds with the (仮). Also, in those meetings WDC “guides” SE to choose some movie that is not listed, even gives him access to unseen footage of those movies to “facilitate” the development. There are other listings with quite a few worlds that were discussed by Disney for inclusion in Quattro but were discarded in subsequent internal SE and WDC meetings.

ML was going to have several unreleased worlds from those discard lists but ML was “temporarily” cancelled.

The SE insider says that the team is “working” to recover all the resources and materials that were made in ML for the future of the saga. As a curiosity, he says that Quattro will have some keyblade or heartless from ML. And Disney has already been able to see some of the new worlds and they have been “pleasantly” surprised, even expressing that it looks much better than the original movie.