Apple TV will soon get a major software update tvOS 15 which was revealed at WWDC recently, and like new software for other Apple devices, you can test the new features of tvOS 15 early if you are part of Apple's public beta program.
But it should be noted that if you install tvOS 15 on a newer Apple TV 4K device, you will not be able to go back to tvOS 14 as you cannot connect the latest Apple TV 4K device to your computer using a USB-C cable.
tvOS 15 supported devices:
Apple TV 4K (2021)
Apple TV 4K (2017)
Apple TV HD
Here's how to install tvOS 15 on your Apple TV?
Open the beta program of the Apple website and sign up for the Apple Beta Software program on your computer.
Go to the tvOS tab after logging in.
Click Get Started and register for your Apple TV.
Open the Settings menu on your Apple TV and tap Users and Accounts.
Make sure you're using the same Apple ID on the Apple TV that you used to sign up for the beta program.
Select “System” > “Software Update” > switch to “Get public beta updates”.
Update your Apple TV from your system settings after enabling the public beta update setting.