Mishaal Rahman: Google is preparing to fully remove support for non-A/B updates from Android, leaving A/B updates as the only officially supported OTA update mechanism moving forward.
Mishaal Rahman (@MishaalRahman@androiddev.social)
Not just seamless, but safer updates as well. A failed boot from the newly updated partition(s) can be detected with the malfunctioning slot flagged by the lower-level bootloader, allowing for an instantaneous rollback.
This could break devices that are older
How many devices are that old but still getting updates?
My 6 year old OP6 has A/B partitions.
Older devices wont break unless you force install without creating the necessary filesystem partition layout first. Depending on how you define older that might only be a small hurdle. If you define it as a device designed for Android 4 you're likely gonna have a bad time.
TBF it's a major PITA to redo the partition table like this, if even at all possible given the extant layout. This was introduced with Nougat, though, with major chip vendors like Qualcomm ready with support in their BSPs right out of the gate back in 2016. I think eight years is enough time to let everyone get themselves up to speed.