The next version of Android is currently known by the codename Android M, but it's expected to get an official name as well as a version number before it actually rolls out later this year.
Although everybody believes Android M will officially be called Android Milkshake (likely due to the milkshake-like illustration spotted on a Google executive's watchface during the Android M unveil event), there hasn't been a lot information to surface about the software's potential version number.
Several reports however have made a discovery that suggests Google wants Android M to be a 5.2 update, rather than a 6.0. Keep in mind Android Lollipop, the current version of Android, launched as 5.0, while KitKat was 4.4, and the size of the jump between version numbers correlates to the update size.
Someone basically noticed a screenshot of a new "demo mode" within the latest build of Android M for developers, and it shows the clock fixed to 5:20. Demo mode hides all icons and notifications in the status bar, and so this system time is not only noticeable but also curiously set to a time that could double as a version number.
Google has used system times in the past to hint at version numbers. A screenshot from Android 5.0 showed 5:00, for instance, while Android 4.4 showed 4:40.
So, it looks like Android M might get the version number 5.2 at launch.