Most likely, Wrestlemania 30 will be held in Madison Square Garden considering every 10 years it's held there. For Example: Wrestlemania, Wrestlemania X, and Wrestlemania XX.
Atlanta
It's going to be held in Miami Florida(:
Rogers Centre Toronto Canada
WrestleMania XXX (30) will be in New Orleans. It will be held on April 6, 2014.
XcelEnergyCenter, St.Paul Minnesota.
New Orleans louisana
It is going to be held at the AT&T Stadium in Dallas Texas on April 3rd 2016
Wrestle Mania was already held at the Nassau Coliseum.
WrestleMania XXIV is the forthcoming twenty-fourth annual WrestleMania professional wrestling pay-per-view produced by World Wrestling Entertainment (WWE). It is scheduled to take place on March 30, 2008 at the Citrus Bowl in Orlando, Florida. The event will be the first WrestleMania to be held in the state of Florida.
There's a debate about where it's going to be held.. But it's going to be in either Dallas Texas or Toronto Ontario (Canada)
The Undertaker is going to retire the next day at WrestleMania 32 when he faces Sting.