I've implemented basic MathJax support in texi2any in commit 7ff3cbdc4. To use it, run texi2any as "texi2any --html -c HTML_MATH=mathjax". Feedback would be appreciated on how well it works with Texinfo manuals containing math typesetting.
I think the main concern at the moment is making sure that the source code for MathJax is easily accessible from pages that reference it, and that users do not need to be dependent on MathJax's hosting.
