Assuming this rumor is true, I'd think Canon would still wait a couple of years before releasing it. Everyone that would buy a camera like this just bought a D800/e or Canon 5D III; and if you're a professional you purchased two or three of them. It will be at least three years before I consider purchasing another camera.
Everyone?? I see a lot of 5D II owners like myself that are not pushed to go to a 5DIII at all. And put off by the pain of starting a Nikon lenses collection. 5K for a camera along these lines would cost the same as a D800 and a 14-24mm lens and I'd be back to using my Canon 14mm L, 17mm TSE L, 24mm TSE L, and 24mm 1.4 L for architecture and landscape. Sign me up!
There are a few possible approaches to take.
1) Recognise that actually owning camera equipment is not very worthwhile unless it is making you money and/or you're using it regularly and then when you need it, rent/hire whatever happens to be the latest/best.
1a) Start up a Nikon lens collection, whilst keeping your Canon lens collection and just rent whatever body happens to be the latest/best/to your liking.
2) Build up an array of Nikon lenses, along with a D800 whilst keeping the Canon gear. Treat the bodies as something that can be sold/traded/whatever. Then you simply sell your older body and buy the new one whenever one manufacturer makes a big leap over the other.