With the start of this generation of consoles, Sony surprisingly snatched up a timed exclusivity deal with Activision with all things Call of Duty, which was with Microsoft and the Xbox 360 last gen. This timed exclusivity deal has gotten a new twist with Black Ops 4.
Source: N4G PC Call of Duty: Black Ops 4 New Content Will Only Be 7 Days Early on PS4, Not 30 Days