The top dog carries the name Radeon HD 5870X2, and we are talking about single-PCB, dual-GPU card that will retail for cool $599. This is still $50 cheaper than GTX280 at the time of its debut [do you remember the outrageous $649?], but bear in mind that this is a top dog part.
For some odd reason, the $499 bracket will remain without a card. We expect that slot will be filled with a water-cooled edition of 5870, or more likely - 5870X2 once that nVidia launches their competing products. Afore mentioned Radeon HD 5870 is set to go on sale for $379-399, while the cheapest entry into the 5800 series, the Radeon HD 5850 is priced in the $279-299 bracket.