Battery saver update changelog had given a clue about availability of Windows Phone 8.1 update Build 8.10.14203 soon and it is here now. My devices have now shown availability of this critical update , that takes the OS version to 8.10.14203.306, and will get installed automatically in 72 hours even if you don’t install it.

The update is not very big in size and whole process should take between 15-20 mins from download to install to backup to restore.