Khan Academy released KaTeX, a library that does essentially the same job as MathJax does today -- only faster. Part of that is probably because (the hard?) part of the layout can be preprocessed on the server. This may also enable mathematics typesetting in apps more easily.
As of now, it does not offer all the symbols and functions MathJax has -- so we don't want to switch now -- but eventually we should consider moving over. MathJax is nice but it is just painfully slow on pages with many formulae, which sites like (math|cs|cstheory).SE have plenty.
Using KaTeX as primary engine with MathJax as fallback will soon be available; this solution would already speed up many a page.
Some site metas have picked this up: