Of course, it could be a different character on the mane-team, but considering all of the evidence so far I think we can probably put this one to rest. I wouldn't mind a screwball though. Bring it on Hasbro!
Update: We are getting reports that there is a Zipp Storm trademark too. Looking into that one!
Update 2: Zipp Storm has a separate trademark on USPTO.gov. We might have two separate characters, or Hasbro wasn't sure what her final name would be.
Update 3: We Also Have "Princess Petals!" My guess is we have two characters, Princess Pipp Petals up there, and another yet to be revealed character named Zipp Storm Thanks to Emperor Sombra and VcSaJen for the heads up