The Samsung Galaxy Note 4 offers a 5.7-inch display with a Quad HD Super AMOLED display and a resolution of 2,560x1,440 pixels with 518ppi.
What will the Samsung Note 5 or Samsung S6 screen be? Why do we care?
We care because the Gear VR and Oculus Rift both contain Note 4 and Note 3 screens. AMOLED is the best technology for VR providing superior contrast ratios (Think inky blacks in Elite Dangerous)
What is 4K anyway? 4K is regarded as a resolution of 3,840x2,160. TVs are already readily available in this resolution as are computer monitors.
At a Samsung analyst event in November 2013, the company did reveal that it was developing Ultra HD displays with a 3,840x2,160 pixel resolution for 2015 with ~800ppi. Given that the Samsung S5 is a commercial failure they may push this into the Galaxy S6 which is expected to be released in March 2015 although more likely for the Note 5 later in the year.
If this is the case then Oculus will already have their hands on early prototypes and perhaps the 4K screen is contained within the highly secretive Oculus crescent bay prototype (Oculus has refused to state what their screen is)
The real question is this. Will the average phone user see any improvement in 4K vs. 2k?
It would be very difficult except for those with 20x12 vision (better than 20/20) to see any difference.
It probably makes little sense to have 4K in a phone if that was the only purpose.
Samsung is most likely thinking beyond just simply phone use but into additional applications like their Gear VR. Imagine how their phone sales would take off if people buy their phone and a cheap $199 VR device and have an IMAX screen in their living room?
Who would buy an iPhone then?