Specs have been leaked though.
ATi/AMD's Radeon X2900XTX
-750/2400
-1024MB GDDR4
-64 Unified Shaders, 4 ops per clock, per shader = 256 effective Shader Ops per clock
-512-bit memory bus
-153.6GB/s memory bandwidth
-Internal Crossfire connection over 2 bridges
By the looks of it, it's going to give the 8000 series a run for their money, as it is more powerful even than the upcoming 8900GTX.