This is the first Google box by Buzz.
Typically Buzz handles both Firmware and app (BuzzTV 6) updates themselves, and they are pushed by OTA.
On this device, the box firmware will be handled by Google. And BuzzTV 6 app will be updated through the play store, by Buzz themselves (like the release an update of any other app on the play store).
BuzzTV 6 get's regular updates now on the PowerStation and L1 (via OTA). So I am sure it will get regular updates through the Play store also.
To get an idea of how long it will be supported, BuzzTV 5, was introduced at end of 2020 I believe, and it is still getting regular updates today on all boxes. Frequency depends on a number of factors, including criticality of any bugs that may exist, time of year (summer vacations or holidays), etc.. Sometimes it is a few in a month, other times it can be a 2 or 3 months, but with a larger update at the end.
Hope this helps.