Usually the pattern is (giving examples from the last generation of ATI releases):
First they put out super-high-end cards that blow today's hardware out of the water but cost a fortune. (ex: R9700Pro)
Then they put out low- and mid-range parts later, which basically match up with the performance of today's high and mid-range parts. (ex: R9500Pro/R9600Pro, R9000Pro/R9100)
Finally, they issue 'refresh' parts for the high-end cards, which are even faster. (ex: R9800XT, R9600XT)
Then the next generation of cards gets developed and put out. (ex: R420/423)
That's how it's gone the last few times around, and I doubt it will be much different this time. The whole PCI-Express thing might change the scheduling a bit, though...