This was buried in another thread, but the release date in Japan is "Middle of July" after the 1dx release.
The important question for me is not when it's released, but when enough is produced to that pre-orders are filled and the price begins to drop. I don't see Canon getting away with this price tag for long due to the Tamron 24-70/2.8 with vc - of course the Canon will be better, but that won't justify 2x the Tamron price tag. I hope the Canon 24-70/2.8 will see a $500 price drop sooner or later.
Thats obviously in the eye of the beholder but it does seem that Canon will be giving up part of the market here, perhaps the mk1 24-70 will be kept in production?