Was thinking about this earlier.
Personally, I'm hoping for a downloadable Mew EX, Mew coin, Mew Playmat, and Mew Sleeves for the TCGO.
But who knows?
http://www.pokemon.com/powerbracket/us/
Everyone can get the Rewards now from the looks of it
Its a wallpaper for your Computer and an GIF (whatever that is)
and of corse the T-shirt at Hot Topic