I would imagine they would be available immediately upon release for the simple fact that people will start gearing up immediately when they hit 85, which will be well before Dec. 14th for many people. It wouldn't make sense to make people wait until one week after release to get non-crafted upgrades. The question would be, why wouldn't the 352 PvP blues be available upon release?
Its all available with the Cataclysm relog (after 00:01) from the regular vendors. Even Vicious gear is available, but there is no fast way of collecting Conquest points until the season starts (1 week later).