This is something of a surprise. We sorta didn't expect Sony's 25-megapixel full-frame serious pro sensor to land in a Sony DSLR. The cam's details are scant as hell—it doesn't even have a name, just "flagship model system." All we could squeeze out of recalcitrant reps, other than what we already know about that sweet sensor, is that it's definitely an '08 release and has a 3.5-inch LCD that's got at least a megapixel of resolution (the a700's screen was name-checked), plus it has built-in image stabilization. Since it's so prelim, no other specs, price or more definitive release date. Looks like the D3 and EOS-1Ds Mark III might have some new competition.
Clearly, Sony's system is still premature compared to Canikon, but they have to start somewhere. They've only been in the DSLR for a coupe of years, they are starting to get some very nice Zeiss lenses at good prices. Perhaps in 5 years they will be the big three, but they first need to have the bodies that can actually take advantage of good glass and build their system up. Competition benefits everyone.
Like I said previously, it doesn't look like Sony is aiming this camera directly full-on at the professional market, as evidence of the prosumer body. But it may offer a lot more value and features at a lower price compared to the competition. Regardless, being that Sony has a long history of supplying Nikon with sensors, we'll likely see this 24.8-megapixel sensor in a Nikon in the future, likely to be more a studio-oriented alternative to complement the D3 which is more suited for sports photography.