It wouldn't have anything to do with spin-offs because Gamefreak doesn't make them.
They've done it before. I think its unlikely to be an event, but its not out of the question.
From the looks of it, seems we are definitely getting either of these:
-gen VI/game announcement
-silhouette of the actual star in M16
This pretty much sums up what I think about it, though I think the second one is more likely.
They could reveal the silhouette on Pokemon Smash and then reveal the Pokemon this month's coro-coro, much like they did with Zorark.