And let's be honest here, any Canon advocate that thinks that Nikon has been blown out the water is delusional. I'm quite prepared to believe that the "D4" will be at least as good as the 1DX and Andy moved from Canon for the 200-400mm, not for the ISO capabilities (I think that was a bonus when he got the D3s).
That was the point I was trying to make - each brand has a 'lead' at a snapshot of time. I would expect Nikon to respond to Canon and then Canon to respond to Nikon. As an amateur I wont be switching as I have over Â£10k in lens and the advantage I would get from moving to a Nikon lens or body would be insignificant. Although I might just buy one to sit alongside the Canons if I had a specific need.
People that move from windows to mac turn into the most ardent fanbois, constantly justifying why they swapped. I suspect it will be the same with Canon and Nikon convertees.