Oculus Rift would be useful in those situations when you want to switch between say a WW1 flight sim[1] and a modern day one. It would be a little jarring to be flying a Fokker Dr1 in from the confines of an F-16 cockpit (well unless you want to pretend you went back in time and suddenly your mach 2 jet fighter must obey the limitations of 1917 aviation). The cockpit + Oculus Rift would at least dampen the sense somewhat of being seated in a modern day cockpit without having to build two (though building a modular one that you can swap the cockpit part in and out might be an idea). Maybe add a programmable fan blowing in front of you that adjusts its RPMs based on velocity to simulate wind effects :)
[1] http://store.steampowered.com/app/244050/?snr=1_5_9__205
I suspect the long term effect will be much like simulators have displaced some recreational real world flying and training, but not as much as you'd think.