You folks are being way too practical in your definition of standard. I was using the "accepted and promulgated by an actual standards body" definition. As distinct from a variety of Microsoft "standards" (can anyone say "DirectX"?), for example. Of course ePub is being pushed by Adobe.
In a more practical sense, of course, being "standard" as in "commonly available" depends on actual uptake of the standard by enough players to cover the great majority of the market in question. And that remains to be seen for ePub. For the moment, however, it is the big hope for reducing the current "Tower of eBabel" effect in the eBook world.