After a weekend of trying to figure out which package update broke my wifi, I finally found this:

https://bbs.archlinux.org/viewtopic.php?pid=1993686

The key part in that post is that after you rollback the kernel update, you have to reset your BIOS to get wifi back.

The kernel update was my first suspicion but rolling that back seemed to have no effect. I discovered something was amiss at the BIOS level when I realised I was a major version behind and attempted to perform a BIOS update via wifi to discover that not even BIOS was able to use the wifi!

The joys of being on the bleeding edge!