WrestleMania sells it self. A majority of people buy it because it's WrestleMania, and not because of the matches. That's why 27 and 29 were record setters, during their time, even though they sucked sweaty butt cheeks.
They're gonna need more than brand name powah to sell 100,000 tickets from now till April 3rd. I don't see them pulling it off no matter who they get on the card, but they certainly can't think that repeatedly telling everyone it'll be "the biggest Wrestlemania of all time" or having Rock say "Show up to watch me do something on April 3rd in Dallas! We'll break records!" over and over will be enough to get the job done either.
I think no matter what the actual attendance is they'll still say it's over 100,000, even if it's really not.