Thanks for pointing this out, I've clarified the docs. Canonical (the company behind Ubuntu) stops free Xenial support on April 2021. There is an option for people to purchase Ubuntu's ESM support and create their own stemcells which will be patched until April 2023 but that isn't something that will be released on bosh.io. We are restarting work on Bionic and you can follow that work by searching our public backlog for stories with the "bionic" tag. https://www.pivotaltracker.com/n/projects/956238