Rumours are pretty rife at the moment that they'll be doing Pokemon Stars, a sort of third version of Sun & Moon for the upcoming Nintendo Switch.
I'm not buying into it entirely yet. They've been doing a lot of things in an unorthodox manner lately so doing a third version seems less likely. After all they've had sequels (BW2) or just no alternate version at all (XY). But at the same time, Nintendo Switch isn't a typical straight forward home console. It has the potential to be taken out as a handheld. Something the Pokemon main games are historically linked with. Hmmm...!
If they do release something for Switch, I hope it takes place a few years later in the SM continuity. A liked a lot of the characters and the world itself was enjoyable.
It's very possible they might do something. After all, there's all those construction plots akin to the ones seen in RBY which were then built up in GSC.