It is not just MP and DR. What about excellent live view, usable LCD, touch screen focusing, great battery life, excellent lenses, decent firmware? I may think that matters a lot.
My dream kit right now? Hartblei HCam with some Canon TS-lenses and P45+. But, it could be a Sony A7r with Canon TS and a Sigma 24-105/4 zoom. Or something else. We are going to find out.
I believe that many Nikon shooters like myself only care about the cost/performance of their equipment, not the least bit the logo on the body.
Considering that my F mount lenses (Nikon, Sigma, Zeiss and Leica) would be mountable on such a Canon high pixel camera with superior DR (nobody would care for 45mp at 12 stops DR), I wouldn't have to "convert", just to buy this new wonder body.