This looks pretty sweet. The next big thing for api versioning would be header instead of url based routing, looking forward to 'give you access to other routing methods'.
Edit: On a second read, it's less clear if header based routing is actually available yet...
"each Application Load Balancer allows you to define up to 10 URL-based rules to route requests to target groups. Over time, we plan to give you access to other routing methods."
The ALB clearly has technical access to the headers, but use of them isn't exposed to users yet.