As confirmed when Modern Warfare 2 was originally announced, Warzone 2.0 is "the new, free-to-play battle royale Warzone," so although it's built on the same technology that's powering MW2 you won't need to purchase that full-price release to get access to it.
Around the same time the CoD franchise hit the 400 million copies sold milestone, Call of Duty: Warzone, which was released in 2024, reached the 100 million players mark. What sets Warzone apart from other entries in the CoD franchise is that it's a free-to-play battle royale game.