DocBook 5.2 is around the corner [1], we use DocBook 4.5 which is 'feature frozen' since 2006, and there are even ideas for DocBook 6.x [2].
I want to inform you that I'm working on an upgrade of our documentation to DocBook 5.2. Major steps have been done, but I need some more time before I can publish a first working draft. Please keep me informed, if someone else is working on the same issue.J. Purtz
[1]: https://github.com/docbook/docbook/releases/tag/5.2CR3
[2]: https://github.com/docbook/docbook/issues?q=is%3Aissue+is%3Aopen+label%3Av6