See, what I think they do is the continue along logical lines. It's clear that Disney is still down for LEGO Star Wars being a thing since they went out of their way to make Lego Force Awakens AFTER their contract with tT was completed. they recently stated that they were pulling out of making games themselves, so it makes all the sense in the world for them to let LEGO use their IP in ways that make them money hand over fist like Dimensions does.
So yes, Harry Potter, but also Star Wars and Marvel.
After those, it may also be worth considering the fact that LEGO put two of their three(now four) personal IP in the first game. What MIGHT be on the way are Bionicle Minifigs and Nexo Knight Sets.
There's also the sets similar to Back to the Future and Ghost Busters to keep in mind. Perhaps we could see the like of John Connor or Indiana Jones.