You will once again need a whole ass drive just for one Call of Duty game.
A soldier with a skull mask standing far above what looks like some sort of facility.

Those who dove into the Call of Duty: Modern Warfare 3 campaign early access have found that their total install size weighs in at just shy of 235GB of SSD space occupied. This is true for at least the PlayStation 5 version of the game. On the PC side, I have my install down to just 101GB, but that's without having Modern Warfare 2 content installed, which I may or may not end up needing anyway once the multiplayer is live.

These massive install sizes are all because Call of Duty: Modern Warfare 3 is now just a part of Call of Duty HQ. This Call of Duty HQ places huge swaths of content behind an all-in-one launcher system, meaning that it includes the Modern Warfare 2 campaign and the Modern Warfare 3 and Warzone and Modern Warfare 2's multiplayer. What it doesn't yet include is the multiplayer component for Modern Warfare 3 and the Zombies content coming with Modern Warfare 3.

Activision has already issued a statement about what is going on with these massive install sizes. They also flatly admit that file sizes are "larger than last year."

Activision notes that players can manually shrink the install size of Call of Duty by removing various pieces of content they are not actively playing or using. This should help clear up at least some space. However, it's not exactly clear what content is safe to remove from Modern Warfare 2 if you want to only play Modern Warfare 3 content as there is a lot of shared content between the two. They also note that the final install size will be "smaller than the combined previous Call of Duty experiences." It's unclear what previous Call of Duty experiences they're talking about here.

Call of Duty: Modern Warfare 3 early campaign access is currently live if you pre-purchased Modern Warfare 3. From what I have seen online, the campaign can be completed in under 4 hours. Perhaps there's just cause for it to be listed as "DLC" after all. The multiplayer and Zombies content will be released on November 10, 2023.