Looks like USUM will be the first upgrade game without a bigger battle facility. We know Tree and Royal return and on top of that Festival Plaza is supposed to have one of new additions "related to Battle System of previous games" as GF said which is rumoured to be factory but we dont even know if this will be a facility or just an option to "borrow/rent" your friends/visitors mons when you speak to them in the plaza

Either way it doesnt look very promising. Other than hat there are no hints there will be anything more and the "mysterious cloud" will probably be just a cloud. We can for sure forget Battle Frontier: Tree + Royal and factory in any shape or form makes Frontier obviously not happening. PWT would require lots of character model so aint happening either

Makes me sad.