I think portability is dramatically overrated.
When exactly is it useful?
During school/work? Certainly not.
When you're at home? No advantage over a console/PC.
On the way to school/work? Only if you use trains/busses (and longer than say 10 minutes per ride).
Is anyone going outside just to play with a handheld? Even then a laptop/tablet would suffice.
And don't get me wrong, 4k is just a bonus.
I've found it incredibly useful inbetween classes at college. Finish one class, don't have anything during the next hour, and I'm too lazy to walk back and forth between buildings in time for the next class. It's a lot more convenient, imo, to just be able to pull out a singular 4x12 inch device rather than a laptop + a controller/mouse if I want to play a game where a keyboard alone won't suffice. Really, I think that convenience factor is what makes the portability so appealing. If you have to wait somewhere for a while, it's a lot more convenient to just be able to use this one small device than a much larger and bulkier laptop.
A tablet would, in theory, carry the same capabilities, but it also doesn't really have any games I'd like to play. Plus I'm pretty sure tablets are nowhere near powerful enough to run most console games, although I could certainly be wrong about that.