My point was the A7R will take sales from the A7S
Sorry, I mis-read your post.
Are you saying the A7R has a good video legacy so more people will upgrade to the A7S?
I was (missing your point) arguing people still buy Canon because it's got a legacy as good video dslrs, but that might change over time once the competition has "pro" features at a decent price. The 70d has nice lv af though which also might appeal to some, but it's on the other end of the "low light capability" scale than the a7s.
I really can't see Sony ever making a serious pro camera. Certainly nothing in the 5DIII / 1D-x product bracket. Their camera design objectives and product placement look confused and badly thought out. For my needs a 1DX or 5DIII are pretty much the best range of features and reliabilty that there is. I trust also the Canon band, which is a lot more than I can say about Nikon, Sony or Sigma. I'm not saying Canon haven't made mistakes, but they haven't isolated me in the market place. If I was in Nikon land, I would still be wondering how I would be upgrading from the D700 within a wedding photographer's context. For me, the 5DIII is pretty much perfect, although 2 stops low noise shadow detail pull-ability would be nice.
There is so much more to a camera than it's sensor. I think Sony's cameras are a case in point here. Great sensors, let down by poor cameras.
When I look at the Nikon lens catalogue, I see a lot of ancient designs, most without USM (or what ever Noik call it). I see a lot of screw driven lenses and very few really new and interesting things. There's some but not many and it's not a comprehensive as Canon's. If I look at Sony, that disparity is even worse.
Anyone who has used the newer 24-70IIL, 70-200IIL or any mk II white super tele's will know what I am talking about. In fact, my 35L and 85IIL still produce fantastic pro images for me, while I hear that Sigma has a good 35mm...I don't trust their reliability or AF capabilities....sorry, but that's been my experiance. there is more to a lens than just flat lens charts. In 8 years of pro shooting, most of my Sigma gear has gone back for repairs or calibration 2-3 times per lens. My Canon gear (which i have more of) takes a beating far better and I think I've only sent one lens into Canon and that was for a front element replacement.