I agree, it's a massive update. Also, their approach to using Linux containers for Android App support should (I think) make it much easier to keep up to date with Android updates. In theory, that would also make it technically easier to support older Sony devices as long as there are kernel and AOSP updates from Sony for those devices.

Note "technically easier", there still has to be some source of income to fund that effort and as those older devices are no longer for sale, there is no (new) matching revenue. That could change if Jolla moves to a subscription model, where recurring license revenue for older devices could fund updates.