I mean it's Disney, they also never really made a lot of merch for KH even though people were thirsting for it, so that's why I'd believe that they are kinda hesitant with it.
But yes, that's another thing I had forgotten to mention, if we only have a few worlds to begin with (I forgot the number, 6-8 was it?) then that means a) some WILL be reserved for revisits of old worlds and some have to show new Disney worlds. That's why I personally believe 2 is really pushing it and it would make more sense to me to include one for now and wait for the reception.
Monsters Inc and Toy Story are definitely the best choices for Pixar worlds, there is no doubt about that.