I am also using 2.9.2 and never upgraded, but did a fresh install of NextGen Gallery 1.5.2. Once I upgrade, I get the same message as if nothing happened.
Below is the message I receive:
Upgrade NextGEN Gallery
The script detect that you upgrade from a older version. Your database tables for NextGEN Gallery is out-of-date, and must be upgraded before you can continue. If you would like to downgrade later, please make first a complete backup of your database and the images.
The upgrade process may take a while, so please be patient.
Start upgrade now…
