So I've been thinking about the possibility of Generation 6.5 happening with Pokemon Z in light of Pokemon Z, and just yesterday, I thought about one possible hint for Generation 6.5 that hasn't been discussed yet: Ash's current Kalos team.
What do I mean? Well, for those that aren't up to date with he Pokemon anime, Ash's team currently consists of Pikachu, Greninja, Talonflame, Noibat (which will soon be a Noivern), and a Hawlucha.
"OK, thanks for sharing me his current team. What's the deal behind it?" I'm getting there. As of this post, he is getting close to receiving his 8th gym badge, but he still doesn't have a full team; it's still just those five Pokemon. With the Kalos Pokemon League matches hinted to take place this year, it seems odd that Ash doesn't have a full team yet (no way is he going into the league without a full team), but why could it be?
I think that they are saving the final slot on Ash's team for a Generation 6.5 Pokemon. This generation 6.5 Pokemon could make an appearance in the anime similar to Helioptile, Gogoat, Noivern, etc. did in the past where they will be revealed by the time they make their first appearance but they will have an appearance in the anime prior to the new game's (the one that Pokemon will debut in) is released, except this time, Ash will catch this Pokemon. It seems like they don't want Ash's team to be complete to hype us up for the exciting new concept of a generation 6.5, and to highlight this new idea, one of Ash's Pokemon on his Kalos team will be a part of the newly added Pokemon in Pokemon Z. It's happened before too. Munchlax, Bonsly, and Mime Jr. joined May, Brock, and James's teams respectively before generation 4 was released.
Of course, it's entirely possible that Ash's 6th Pokemon will be a Kalos 'mon we already know, but considering where he and the gang are currently are in Kalos, I don't think there's too many options. Then again, this is all just speculation, but I can't help but think of the possibility that the writers might know about what Pokemon Z has in store and are purposely not completing Ash's team right away so that he could obtain a Generation 6.5 Pokemon as another way to advertise Pokemon Z.