the financial reporters are estimating the first gen of hardware at roughly 1M cv1 units for oculus, and a hodgepodge of htc vive, newly renamed sony PS VR(formerly morpheus), hololens, gear vr for a total number just under 10M.
most people's first experience will likely be gearVR or google cardboard.
the hardcore VR gaming contingent will go rift or vive. certainly all the Elite and SC space jocks will be gaming on release day.
the wildcards will be ms hololens and sony psvr. they could make or break the inbetween markets, which may sour people on the vr experience.
castAR may be a darkhorse in the casual market. a group of friends sitting around a table in a club with a shared 3d game could really change perceptions.