Having just done a little [more] research to refresh my memory of TeX, and to find out a little about MathML, it's a no-brainer.
The next ePub specification needs to include [presentation] MathML as a required component. I'm not entirely sure without looking into it more deeply than I want to, whether content MathML is needed.
http://www.mathmlcentral.com/history.html is a fairly succinct summary (granted, from what might be a biased source). There seems to be plenty of work going on on ways to get TeX quality typesetting from MathML expressions, and the ability to copy/paste from MathML to ctual methematical evaluation software seems an important ability that any purely layout based system (i.e. TeX) can never match.
It is possible to typeset equations using an SVG graphic, but these are awkward to create, and only a little better than a bitmap version.