Something tells me down the road DSLRs will always have video but something will emerge (2-5 years+) that is predominantly focused on video but can use DSLR lenses for the same price. I think all the "rigs" people are selling to make DSLRs a usable dedicated video camera indicate the direction or the opportunity for companies.
I said that a year ago, looks like I was off by 1-4years ;)
Canon, Sony, Red, Black Magic, and I saw some rumors Panasonic is planning a primary use video camera to use their m4/3rds lenses as well - maybe they already have. There will be more - and soon with their smaller MP sensors, someone will create one that can have clean video way beyond any DSLR can do now. With all the accessories, it seems pro videographers are trying to turn DSLRs into video cameras. From what I keep hearing, many just want the lenses and the limited DOF. Few care less about the body style.
Video is limited by much more than photography just by the TVs available to video formats the broadcast system and handle that will determine their course. 4k TV video is just coming on-line (4096 × 3072) and that is only a 12.6mp sensor image. By last count, every DSLR released in the last 6 months has not been below 16mp. Where everything gets interesting is that MP count is still rising which would seem to limit clarity of high iso video where Dedicated Video systems can continue to refine 3/6/10/12mp sensors and produce cleaner images.
DSLRs will always have video and there will be a use for it, but I'm sure more affordable primary video systems will become available that can use DSLR lenses, have similar or better IQ and better audio controls and people will flock to those. Then we will see the separation again, but never exclusivity of just one or the other in a system.
Maybe I'm way off, but that seems the direction everything is moving from what I have seen.