Surely Canon must be looking at the 1D MkIV and the 7D and wondering why sales of the 1D haven't been affected when they have with the 1Ds & the 5D MkII. Surely price must be a factor, is the 1Ds really worth Â£4500 When the only really difference is the sensor thats over Â£1000 premium over the 1D and the price of that hasn't really come down since its launch, in the days of the MkIII it was Â£2000 dearer.
The 7D doesn't seem quite as well built as the 5D MkII which could play a part, and I wonder if Canon will downgrade the MkIII to 7D standards to create a wider gap.
I think though that the biggest problem here is the different uses the cameras have, the 1D is a real action tool, sports, journalism, commercial photography, where it needs to be able to handle all that hard work can throw at it, wheras the 1Ds is better for studio & product work where life is much more comfortable, and it's build isn't quite so important, you could go through 3 5D MkII's for the price of one 1Ds
Canon has a choice, it either cheapens the 5D MkIII which might not be popular especially if Nikons D800 has a decent sensor, or it uprates it and drops the 1Ds line. Of course if could carry on as it does now with the 1Ds as an expensive niche product.