The frame rate is not divided by 2, the resolution is. 960x1080 per eye at 120fps.
The 120fps can be reached with motion interpolation. Sort of like how 120hz motionflow tvs work, except in this case your head movements will be updated at 120fps. There can also be games that run at 120fps natively, but that's not a requirement.

between the resolution being 1080p on an OLED display and it being 120 Hz has me very optimistic but it also has me thinking this will be premium priced and therefore out of reach for the majority of PS4 owners.
If they can't get this into peoples' hands then content creators won't have a reason to make content.

I'm excited to try it and maybe even buy it but this could end up being a situation where only a few people get it right away, a few games come out for it and the sales are poor so devs back off making content and those who are waiting for a price drop or to see if it is worth getting ultimately pass on it because of the lack of content.

Sony cannot pull a Vita here. They have to show a commitment to this for it to be successful and/or be willing to take a significant loss to get on to as many heads as possible.

Comes down to price and games as always. $200 and decent line up will have attention. $300 and little support no issue passing on it.

I just had a brilliant idea, Rollercoster tycoon exclsuive for PS4, build you theme park, then RIDE your attractions. See i doubt they can come out with more than 2 killer morpheus games but if they can populate the platform with really clever games or a plethora of decent games ( as seen with the ps4 so far) then morpheus could do pretty well

$400 and racing in VR, sold. This tech is not going to be sold for $200, not a chance.
Word of mouth will sell it once people get a chance to experience it.

refreshrate is only halved in stereoscopic 3D, because both the right and the left eye image are shown on the whole (TV/Monitor) screen and the glasses split up the frames ment for right/left eye (either by shutter or by light polarization)

in VR headsets the refreshrates aren't split up, because the eyes either only get half of the screen (1 screen) or both have their own screen (2 screens)

Considering the series has been PC exclusive (besides the first game to Xbox and PC) Id say that's a dick move to PC users, it's a PC exclusive franchise that shouldn't be bought off by a console company just to suit their expensive VR and besides there are now two VR teams on PC with Valve for their VR and Facebook with Oculus Rift, those two would better benefit with the RT franchise, Sony should make their own which could become something new than buying a franchise and denying the original platform let alone others.

i would like to see the return of colony wars or g-police type games with that device. with something like that i'd be willing to spend up to 1000$ for that device.

DAY ONE !

Sony can buy whatever they want.  No different than monster hunter switching from nintendo to sony,  tomb raider to xbox or banjo from nintendo to Microsoft.  Having said all that it ain't gonna happen and chances are,  as you say they should build their own and probably will.