Honest question, does 4K and up really make sense for private use ? I am pretty sure from the distance that you usually watch 1080p content, you wont see a difference to 4K content at all. Of course for big presentations and conference setups i see the usecase, just not for the consumer mainstream. 4K would also set back game console performance by a huge margin, if they will ever adopt it. So i am not really convinc…
But Amazon is selling 75" TV's in the UK, and 100"+ projectors. As screen sizes go up, people won't be too happy to see dpi drop again.
We are also becoming accustomed to higher DPI on our screens via tablets etc.. After I got my phone (1280x720 on a 4.7" screen) my 1920x1080 on my 17" laptop was suddenly noticeably grainy. My full HD 42" LED TV is no longer nearly as impressive as it seemed when I got it and compared it to my old TV.
My next phone will be a full HD 5"+ model, and I expect my next tablet to be in the 2500+xwhatever range or more for a 10", because anything else will look worse than my current phone. For a lot of content, sure, you won't notice much difference - I quite happily still watch my DVD's on my full HD TV.
In other words there are plenty of situations where we will notice the difference to 4K, even if we'd be perfectly happy with 1080p if we didn't have a higher DPI device to compare to.