I once PM'ed a Disney CM who is not with us anymore about the different parade buildings, and they had the following to say:
Al Lutz has made it sound like the Paradise Pier building's days are numbered, because its site is currently being eyed by WDI as a spot for a future attraction. Does anyone new if there's a spot where a new parade building could be built, if Disney ever wanted to take down one of the existing ones?The building behind the Carsland rockwork(with the wavy design) is currently empty. The only thing it's used for right now is the control room for WoC and storage. It used to house DEP, but since it's no longer with us, it's empty. The other parade building behind screamin, is still in use for PPP's floats and smallers floats for the Halloween party and stuff.