Stuff is going on with the website. Beyond that, it's too soon to say.
As far as switching documentation systems, there are two serious concerns:
DocBook is semantic markup. The markup defines what something is, not how it should appear. Most of the other systems that people suggest (rST, Markdown, AsciiDoc) are not. They are easier to use, but much less powerful.
There is no technical reason that a navigation sidebar could not be generated with what we have now. It's really just an expansion--we already generate HTML, this is just more HTML (plus probably additional Javascript and CSS). The problem is getting the knowledge to do that in one place and properly motivated. There might be someone already doing that with a similar doc toolchain. Pointers would be welcome.
The Sphinx systems I've used with the sidebar make it seriously difficult to bookmark a page and then get back to it. I don't know why that is, but have encountered it more than once.
