What differentiates it from the 1DX?
Shutter / body life (let's say you need two 5Ds to get the life of a 1D, then you pay similarly), build (as in sealing, resistance and precision), 12 FPS, a larger battery life and more physical buttons for a more efficient workflow, dual card support.
A 1D is a camera like a Mercedes is a car (I'll keep the Bugatti Veyron comparison for medium format). They are for people who know what they want / need.
These rumored specs seems too good to be true for $2700
Canon knows how well 5D2 sold, they know how much interest 5D3 has generated, they know that people will buy this body in droves. Ever since this website came to life, the 5D3 was the most expected thing; just look at this thread - 7 pages in a few hours, all threads about 5D3 have pages galore. Canon exists to make money. With these specs and this price they know that they will make more than with a lower specced body.
You should also remember that just before the tsunami, there was a rumor about the new 5D having a different sensor than the new 1D. Then again, it was just a rumor, like this one.
P.S. Come to think of it, I think that rumor didn't say 5D, but one other high-end body.