Xbox Series X will let you uninstall parts of games to free up storage space, while still playing the parts you want.
The new storage management feature is coming to Xbox Series S as well, and Xbox director of program management Jason Ronald explained in the latest Xbox Podcast that it's an optional feature which developers will be able to opt into. Improvements like this should help make that 1TB of built-in storage go a lot further.
"Even beyond the hardware, we've actually made user interface improvements to make it easier for you to manage your storage," Ronald explained. "As an example, one of the new features we're adding is actually for, if a title chooses to support it, the ability to selectively uninstall different components of the game."
"Let's say you play a campaign as an example, and then you want to focus exclusively on multiplayer. If the developers chose to support it, you can actually uninstall the campaign itself, so that you can be more in control of how you're actually using your storage, so you really get the most benefit out of the available storage that you have."
I could see this being especially liberating for everybody who likes to keep games installed in case they want to jump back into multiplayer with friends, but are already finished with the campaign. Hopefully the majority of big games make use of this feature - I'm looking at you extremely hard right now, Call of Duty.
Now we know how much of the Xbox Series X's 1TB SSD you'll have available for games, as well.