Sonys new 4k phone thoughts

as I am sure most of you know, the new Sony xperia Z5 Premium has 4k so is it pointless
To me, it looks like a gymic, it is a breakthrough technology but for the average person, I think 1920x1280 is just fine for most people, and a problem I see, this is going to be only one of a few 4k phones, so when it comes time to replace it, you probably need to go back to a smaller res phone, which may not sound like a problem but it will be annoying.
All this is, is to show off, for some publicity for Sony.
Being a Z series phone, it is waterproof which I love and is very useful for me as I do a lot of watersports, it has a the top processor for 2015 which of course the snapdragon 810, which is  a razor fast professor, so specs won't let you down and neither will the camera with 23mp.
As with a lot of phones coming out is 64 bit which means nothing really.
Going back to the display, it is 5.5 inches which to me is ending the realm of what a phone is.
As I said all it is is an overpriced experiment to get the blogs talking.