They will probably have a menu with different ways to use the headset so you can choose. No doubt there will be other control methods coming along now, keyboard and mouse just won't cut it for much longer. Some kind of LEAP controller (version 2 maybe) for the entire torso or something like that that will allow you to hold your hands out so you know where your weapon is in relation to your head and body.
I don't really see the kb/mouse going away for a very long time, we have to accept not everyone is going to get all these new methods of aiming and to be fair, finesse and accurate movement on a mouse pretty much trumps all that.
While it's a stepping stone, holding out my hands grasping nothing but thin air and actuating invisible objects with every little shake/movement vs mouse, I know which I'd rather pick. It's why physical guns/on screen shooting went the way of the dodo in my opinion, it's great for some short term fad, long term it's awkward.
(MP wise)
The other issue is movement, WSAD is simple, mouse to aim equally so.
When you use up your hands for holding in game items, where does movement go? when you want to type or do we really expect everyone to be using voice comms and switching between control methods just to facilitate what we have already.I love the idea but realistically it sounds bad in action.
For me it's Accessibility, Price, Fidelity and Support, if it's a solo game then some options are viable but if it's a mp game where I can just use a kb/mouse then I've already had enough experience with controllers/joysticks/tracking etc to tell me what works and what doesn't, what wins over another method.
Edit: Although I do understand these are stepping stones to something better.