While it can't be said for sure, I think it's a safe bet that the Kalos Starter Set will be in the next format. Most likely it'll be a "Let's get rid of everything Black&White" rotation.
We players shorthand things like "BCR-on" and potentially "XY-on," but TPCi is much clearer when they make they announcement. There will be a page like this one for the next Standard Format that will explicitly tell you what's legal. There's really no way to tell at this point, though.
