When is L4D 3 coming out?
There's no confirmed date. In fact, L4D3 hasn't officially been announced. There was supposedly a leak with information on a L4D3 and HL3 project, but valve has already denied is to be true.
Several, several years from now.
When is portal 3 coming out? Or half life 3? Wanna know? Never! ;-; because valve hates three