What do you want to learn? If you want to know how to use Kubernetes or extend it with custom resources or APIs then I would suggest using EKS/GKE. If you need to run Kubernetes on hardware and understand how to set it up from scratch then old computers is a good idea.
I don’t have any plans at this time. I will want to keep the book updated and maybe extend it or publish a 2nd edition but that will be up to the publisher to decide if it’s worth it.
Google is going all in on progressive web apps and currently working on native container support on ChromeOS. I wouldn’t be surprised if by the end of the year it’d be dumb to NOT have a Chromebook. Especially if Apple can’t stabilize macOS and keeps adding unwanted features to their laptops.