I think they're really delaying to send a BIOS update to reviewers along with updating their cards at the plant to have a higher clock speed. They may also be still pondering pricing. I imagine that's a tough choice. How close to $400 can they go and still be profitable? $450? $400?
They planned on having a huge advantage with the R9 290 in between the 770 and 780, but now it's going to be right on the R9 290's bumper with a decent bundle. Plus, I wonder if they aren't about to dump the reference design altogether and just let the OEM's use their custom coolers out of the gate instead.
It really seems like nVidia may have pissed on their hushpuppies with that rather incredible (for nVidia) price drop. I don't think I've seen nVidia do anything as reactionary as that since the days of the 280 and 260 being way overpriced before AMD arrived with its "keep it small" design philosophy (that they then abandoned after two generations). I think that was the last time nVidia was compelled to drop prices by so much so rapidly.
Competition is grand.