“Dawnguard™ is the first official game add-on for The Elder Scrolls V: Skyrim® – the 2011 Game of the Year. The Vampire Lord Harkon has returned to power. By using the Elder Scrolls, he seeks to do the unthinkable – to end the sun itself. Will you join the ancient order of the Dawnguard and stop him? Or will you become a Vampire Lord yourself? Featuring an all new faction questline and locations, the ultimate choice will be yours.”
Regrettably, Dawnguard has not yet come out for Ps3, but I wouldn’t be surprised to see it in the coming months.