It looks like they're taking registrations for this years arena tournament:http://www.worldofwarcraft.com/pvp/tournament/index.xml
As far as I can tell, the Armored Murloc pet you get for participating in 100 matches is identical to the one awarded last year, so I have no interest in participating this time. But for you pet collectors out there, you've got another chance!
Alliance: Winston, Yungi, Pellinore, Tebyalyublyu, Theadora, Vasili, Winella, Winstonia
Horde: Grotar, Swiftslice