The Nikon D700 is closer to replacement than the D300S. I don't see Canon letting the Nikon D800 (?) have the entry level full frame market to itself with a new model for long.
I wonder if this is part of the reason they have not released the 1Ds IV, as to not tip their hand on the next generation of full frame sensors.
Yeah, I guess we're all waiting for the showdown at Photokina
I also agree with you that we probably won't see any 5D3 until D800 hits the shelf - what a pity.
As for the 1Ds line, I think it's going to be really murky since Canon would not only have to deal with a potential D4 (though I doubt Nikon's in any kind of rush since the fullframe D3s is still considered fresh and usable), but also with the 645D from Pentax.
Of course, we'll see if Canon is going to differentiate between the 1DsIV and 5D3 in terms of pixel counts.