That's 2 years of the upstream LTS kernel. I would expect that major Linux distributions such as Redhat RHEL and Canonical's Ubuntu would continue to do their extended patch cycles against one of the upstream snapshots as they have done in the past. I think 2 years for upstream LTS is probably fine if the vendor patching methodology remains true. This also assumes that the usage of smaller distributions such as Alpine are more commonly used in very agile environments such as K8's, Docker Swarm, etc... Perhaps that is a big assumption on my part.