Xiaomi announced the new version of its OS, the MIUI 7 back in August. Immediately, the developer versions of the OS were available to download to the users. Now, after nearly two months of testing and optimization, the stable versions of MIUI 7 will start rolling out from October 27. This means, you will soon start getting notifications for an update to the latest MIUI 7 version.
The company is offering two options to its users to install the new UI update. You can either wait for the notification to hit your devices and update your phone to MIUI 7 via OTA update. Or else, you can go to the MIUI Downloads page and manually download the ROM package for your device. The ROM builds will be available to download on the same date as it starts rolling out to smartphones.[source]
In case you are wondering which phones will get the MIUI 7 update, the company will release more information in the coming days.