As to what may or may not be released in the future, although we don't know anything concrete I think WotC has given at least a few clues. For example the photos inside WotC headquarters they shared fairly recently, one with a comment about 'Oh what's that greyhawk book doing there on my desk' or something to that effect.
I think they will release adventure paths as they have said, within the iconic D&D campaign worlds. They may release accompanying campaign world books of some sort. And if the very pointed comment tagged on the aforementioned photo is anything to go by, my guess is the next campaign world on their list is going to be Greyhawk.
I place my flag in the sand.