So, uhm, a more reputable source than Latino Review has posted what appears to be a look at this Inquisitor. He's holding Vader's mask, and looks like a Terminator himself. I'm not happy about it, but we'll see how the execution goes -- if this is even true. I hate to pull the "it's Disney" card, but this makes total sense to me. Cross-promotional material between Rebels and Episode VII is going to be a cinch if the villains are in the same sort of league with one another. This is the company that gave nearly every successful movie they had in the 90s a cartoon spin-off, after all. I'd bet Lucasfilm would have taken this approach on their own, too, to be honest. Good marketing towards kids and establishing lifelong fans without necessarily alienating everyone else, provided the film turns out good.

I tend to trust moviepilot, but I have bias as an acquaintance of mine is an employee of theirs. Take that as you will.

edit: noticed that the latinoreview has since updated their post with the same image found here. They're citing indierevolver as source, same as moviepilot. Guess we'll see.