This sounds promising! Transaction wraparound autovacuum is a particularly nasty pathology because it is so devastating and strikes with so little warning: a system transitions from entirely fine to one that is entirely (and mysteriously!) non-functional in a single transaction. And because the system needs to be up for a pretty long time before you see this (it is tautologically rare), many only learn about this failure mode the hard way. Certainly, we at Joyent got completely nailed by this -- and if you want to get a sense of how disorienting this failure mode is when you're seeing it for the first time, read our postmortem of the service outage that transaction wraparound autovacuum induced.[1]
A long way of saying: this is a nasty failure mode, and it's terrific to see the PostgreSQL team tackle it. While there are still some questions (e.g., this sounds like the autovacuum is still kicked but that is at once more aggressive and more intelligent, but does that mean that an exclusive lock on the table is still blocked for the duration of the operation?), this is clearly a big leap in the right direction, and (more) validation that we've made the right choice for our transactional data; thank you PostgreSQL team!