Was the Lubavitcher Rebbe the Messiah?
Maybe. It depends.
If you look at the top of the page of this article on the official Chabad Lubavitch website, it has a banner that says, "Long live our master, our teacher, our rabbi, the messiah king, forever!"
But if you look down below at the article on the page, published today, you find the question and answer on the topic of, "Why hasn't Moshiach come yet?"
Confused? You should be. He was, he wasn't.