IMO, Nikon's choice is a good one... There are situations where the D5 will shine, the others that it won't shine, surely the pro has kept a D4 (not D4s) in the bag for those cases as pros always work with more than one camera... In fact, I think that Nikon saves money from pros in a way, as they will usually buy only one D5 body keeping their older camera along it...
But think of it....
Football games with long telephoto, F1 racing in bad whether, moto cross in the mad and exhibitions too, Night races, natural disasters, night concerts... Then is Nikon's traditional "specialism" from the 60's... the war reporters! There is no point in doing some things as good as the previous model would achieve, as then, there would be no point for the reporter to add the new camera... OTOH, dual interface won't improve things because a sensor that has been mechanically designed to achieve what the D5 is designed to do, won't perform like a D4 at 400 ISO no matter what the interface is. Now, as it is, the reporter can have a D4 & a D5 in the bag and do any reporting better than anybody else or any other camera combination can...