Like your schedule isn't affected by what your competition is doing I believe they can afford to wait a bit and tweak a few things so the match against 570 is won without a doubt. And by the way, nobody but a few know for sure, so what you and I believe doesn't matter much in the end
There is a vast difference between thinking and believing.
I also believe that the delay was not due to 580 and 570 appearing, their performance numbers were estimated quite well in the middle of last year when a 512CC 480 was expected to appear.
Don't you remember the "Cypress is not meant to go up against GF100" messages?
It would be idiotic to think that the launch of the 580 (and announcement of the 570) caught AMD completely by surprise because, in your line of thought, AMD might just as well have to down-tune Cayman so that they don't look so ridiculously fast.