It's going to take a while for mastering rooms and pressing plants to figure out how to do this with any level of certainty. Studios are not going to want to throw away their new digital gear and start over. Refer to the my third point. They're just now starting to pay for the stuff they're currently using. Oh sure, a few exotic labels will embrace this expensive technology, but the vast majority of users are going to use what they have until they make it pay for itself.
Consumers are really confused as it is.
Between MP3, DTS, Dolby Digital, DVD and now SACD, it's really a mess. Frankly, I don't want to relive the Beta vs. VHS thing again. Of course, Sony does have to worry about losing that valuable compact disc logo on the new DVD discs. You can't tell me THAT'S not a significant motivator in itself. Dolby has a lot to lose also.