There are plenty of Chabadniks who do believe the Rebbe will come back as Mashiach. Look at the quote I posted earlier, from the Rosh Yeshiva of the Chabad Yeshiva in Cincinnati. Here it is again:
“The constant focus that this concealment is temporary and that at any moment the Rebbe will return and take us out of Galus. This is the greatest source of optimism, excitement and connection. This is the ultimate driving force in the Hiskashrus of a Chassid today. It also creates the true feeling of accountability to the Rebbe, which is so vital and important for every chassid.
…
Iyh we will be reunited with the Rebbe, Vehu Yigaleinu, and there will be no need to have this discussion!”
The article is titled “OUR POST GIMMEL TAMMUZ BOCHURIM NEED A REALITY CHECK”, by Rabbi Gershon Avtzon. You can look it up.