Just look at who most widely uses the 1DX and D4 level cameras. Sports, journalists, and wildlife shooters. It a ridiculous ratio favoring Canon. People that deeply invested in such a system aren't going to jump to a Nikon in large numbers unless it is so absurdly superior to their current 1Dx rigs and even then it would be difficult. Just look at the CR post yesterday about the journalism awards. It's something like 60-70% Canon systems and then everyone else? That is not a market that easily converts I would imagine not just because of the bodies, but largely because of the glass. I would suspect any limelight a D5 would enjoy is going to be very, very short lived as Canon will almost immediately begin to leak specs of a 1DX2 just to pee on Nikon's little campfire.
Definitely, and it's not just the glass and bodies. The menu system is very important too. When you are on the sidelines of game, it is important to know your camera as well as you know your wife. You need to know how to get the best out of her, and switching camera manufacturers would mean learning an entirely new menu and button system.
I know a couple of part time pros that made the switch but they did not have any big whites, all their glass was wide angle or max 70-200.
When I am at a game, I will talk to my friends about their Nikons and their lenses, but I am not going to switch, and I doubt they will either.