I bet amazon is closer to this decision than some people might think.
With the migration to webkit a lot of the code they need for ePuB support is ready in Kindle 3. The tools available for ePuB and SVG creation has also advanced significantly.
IMHO Bezos's comment on the lack of support for the ePub format to USA Today means just what he says and nothing more than that. It's just a statement on the NOW.
Btw. It's about a year since Sony announced that they were going ePUB all the way
Also check out the recent entries:
http://www.idpf.org/membership/currentmembers.asp