World of Warcraft is scheduled to a see a patch that allows players that are testing the game out in its free-to-play form the freedom to play as an race, regardless of version. Patch 5.0.4 has a bunch of features that you can find here, however the option to play with the Pandaren race in free-to-play mode will occur once the Mists of Pandaria expansion arrives for the MMO.
It is worth noting that the patch only opens up all races for these free-to-play players, the classes specific to expansion packs like the Death Knights or new Monk class will need the expansion content to access.
The new Pandaren race will become available to all when the Mists of Pandaria expansion arrives on Tuesday, September 25th.
Mists of Pandaria Cinematic