Sony have announced via the US PlayStation Blog that Killzone 3 will be coming out on the 22nd of February, 2011 across North America.
It'll come with full 3D support, which looked amazing when we saw it at E3 2010, as well as new weapons and new unit types.
Sony are currently showing off the game at PAX, but they gave no indication of a solid release date for Europe. The only thing we know so far is that the game will be coming out in February as well.
Source: PlayStation Blog