You are right but I wonder if it is any improvement at this point. Writing this on a iPhone 6s Plus and I can't possibly see individual pixels. What is the benefit of going higher?
This is a niche answer, but you can put them in a VR headset with lenses that spread out the screen over a much larger fraction of your visual field without looking too pixel-y.
Hold your 6S Plus up next to a Note 7 viewing the same photograph or high resolution video. If you don't see a large difference, head immediately to the optometrist.