Microsoft has announced today that the Xbox 360 store will officially be closing on July 29th, 2024. After this point, you'll be unable to purchase new games, DLC, and "other entertainment content" from the 360 marketplace.
"On July 29, 2024, Xbox will stop supporting the ability to purchase new games, DLC, and other entertainment content from the Xbox 360 Store on the console and the Xbox 360 Marketplace (marketplace.xbox.com)
Related to this change, the Microsoft Movies & TV app will no longer function on Xbox 360, which means TV and movie content will no longer be viewable on your Xbox 360 after July 29th, 2024."
Despite the closure, you'll still be able to play Xbox 360 games and DLC that you've already purchased, which includes the ability to re-download that content in the future. Backwards compatible titles will also still remain purchasable on the modern Xbox Store if they're available on there - hundreds of them already are!
Online multiplayer won't be affected by this, and even cloud saves will remain. So basically, it's just the actual Xbox 360 marketplace that's shutting down in July of next year, along with the Microsoft Movies & TV app.
Here's a bit more information on the reason behind the decision:
"A lot has changed since the Xbox 360 launched in 2005. Technology has evolved, expectations from players have shifted, and we are focused on making Xbox Series X|S the best place to play now and in the future.
What has not changed is our commitment to preserving your ability to play the content you have already purchased on your preferred device, which means we are committed to supporting Xbox 360 gameplay for the foreseeable future – and you will still be able to play and re-download previously purchased content and connect with friends."