Some good points. One interesting thing to bear in mind is that the pro-DSLRs normally have a long product life - typically over 2 years - and so have less ability to respond to new technology than do lower end DSLRs. Once the Canon 1Ds mkIV comes out that will probably be it for the Canon pro-DSLRs for the next couple of years - leaving only the lower level 5D mkIII as a means with which to implement better video. Because the Nikon D3 series have had only minor upgrades it does leave the door open for a complete replacement.
I think one of the things that is likely to change in the near future is the image processors in DSLRs. Currently most of the image processors were probably designed solely for stills and the manufacturers are just using what is there for video. The next round of image processors are likely to be specifically designed for video and this could result in a big difference in the way DSLRs handle video. It will be interesting to see if the 1Ds mkIV uses Digic 4 processors, or changes to the Digic 5. When the Digic 4 processor appeared in the 5D mkII it was strongly hinted by Canon that this was a stop gap on the way to the Digic 5 (V), but it is interesting that so far the Digic 4 is all that has appeared, even in the long product life 1D mkIV. Newer image processors could aid something like the capture of video RAW. The manufacturers appear to like sharing components like image processors across across their DSLRs, presumably because the scale of economy thing ensures much greater profitability with electronic components that are produced in great numbers. The cost is all in R&D and not so much production.
