AveranNice to hear about the security updates for the 5. That's more than I would have expected. I would happily stay on A11 on the 6 for an extra year if it's getting security updates.
Right now for Zenfone flagships Asus has a 2 android os upgrade policy and around 3yrs of security patches and bug fixes can confirm the latter myself (using an Zenfone 5z right now) my 5z is around 2.6yrs+ old now and is still getting OTAs every 2 months
Regarding android 12 for the Zenfone 6 I think it's rather unlikely as Asus doesn't have a 3 os upgrade policy yet not even for their 2020 phones so unless they commit to 3 os policy nothing can be said about this
Plus even if 2021's Asus phones have 3 os policy then if it'll extend to the Zenfone 6 is a different matter altogether
Android 11 may very well be zf6's last major os version but you guys still can ask for Zen ui 8 whenever that comes I guess