The show starts in 20 mins and will be a half hour of.... well we don't know, but probably/hopefully new music by our faves
Anyway they're playing music in the run up to it now and they just played a Nicki Minaj remix of Single Ladies and they're currently playing Britney's Telephone.
From the hints & rumours then we may get:
Something to do with Britney Either Teenage Dream (song) or the Fingerprints video by Katy Perry
Glitter & Grease by Lady GaGa
Edit: well that was a load of pants, all we got was one line of Britney Spears - Apologize