Call of Duty: Black Ops 3 will release on November 6, 2015, according to some seemingly leaked GameStop pre-order materials. The promotional cards posted on NeoGAF also note that pre-orders will be rewarded with access to a beta, available on PC, PS4, and Xbox One.
November 6 is on a Friday, rather than the traditional North American release date of Tuesday - though it's clearly from a North American promotion, since it features an ESRB Rating Pending logo. The overall release timing is standard for Call of Duty.
Activision plans to debut Black Ops 3 itself (rather than another teaser trailer) on Sunday.