In an interview with Twitch, Treyarch Producer Miles Lesile stated that there are dogs in Call of Duty: Black Ops 4, but not how you might expect it.

The trailer for Call of Duty: Black Ops 4 did tease a dog running through, and many just assumed it would be a scorestreak in game.

However, dogs are an ability limited to a specialist, specifically Nomad. Nomad has the ability to call in a dog and set it to guard mode or attack mode in game.

SOURCE: Twitch