I've seen the efforts of several members of the wiki as they try to get Disney to consider a spin-off, reunion, etc. I'm making this forum to discuss some of the things that get lost in the comments, such as when we can expect answers.
Drawing on what I know, it takes time to develop a show and generally the public doesn't hear about it until the main cast and writers are hired. I'm guessing here that we'd have to wait possibly a year or more until we hear any real news about SIU. The sets were all taken down and some of the cast no longer have contracts with Disney.
Now onto what we can expect, as far as I know, Bella and Zendaya may be out of the equation entirely. Bella stated that she wasn't sure that she wanted a lead role in a tv show for the time being, although she could guest star. Zendaya is currently working on her new show and if it is ordered by Disney then she won't be available to do more than guest star. Basically, it would be a spin-off based on one of the side characters or all new characters in a similar environment.
As a last statement, I don't know exactly what she meant, but Bella did say something along the lines of politics being involved since the creator of SIU is creating Zendaya's new show. I'm not sure what she meant by that. It might mean that a spin-off or reunion will not take place as long as Zendaya's show is under consideration or on the air.
I'm just curious what your opinions are. Realistically, what do you think a spin-off would be about? Are SIU characters or SIU universe more likely? Who would it feature? When do you think a spin-off and/or reunion will occur? Do you suppose Disney might consider a movie option instead?