Exactly. What is the user benefit? There is none that I can see.
Now if they are using some new screen where the touch points are in the pixels and thus doubling it would make the screens even more sensitive and we can write without looking like first graders etc, okay.
But doubling the pixels just to have more pixels is spec wanking and that's not Apple's style
The benefit is sharper, more realistic looking content. Even past 300 PPI. But the higher it gets the higher the ratio is of power consumption to quality. So at some point it will become problematic.
The trade off with this hypothetical 5S would be a somewhat improved display with substantial increases in power consumption and less "oomph" for game developers due to the higher resolution. Which isn't worth it.
Aside from that I'm thoroughly against "doubling the pixels" simply because that would be another resolution for developers to support.
I'd like to see a 5.7 inch iPhone at 1704x960. That's 343 PPI. Easy for developers to support too -- it's the same process as it was from the 3GS > 4.
Ok, so looks like none of this came to pass.
Nope. It would be a very stupid move if it did.