it's kind of hard to believe it's a "typo" when the 1D Mark IV is actually called out like two lines above the 1Ds Mark IV
It's not just that, how they can do a typo on size and weight too ? As you say, it is also positioned under the 1DsIII, and it is not occupying the spot of another camera. Check the 500D/550D for a real typo !
Also, now I think that this can't be done on purpose for traffic generation, as how they are going to explain this to Canon ? by telling them it is a typo ?
The timing is perfect too, I expected the 1DsIV during 2011 Q4, and Nikon are going to do an announcement on 24 August, for which it is rumored 2 FF cameras. I think one of them it is going to be the D3X replacement, the competitor of the 1DsIII.
I usually rarely give credit to rumors, but this one I am going to declare that it is true................................................ Maybe !!