Yeah I'd say the 144hz is one of the bigger/biggest reasons. I'm not sure if you've used 120+ hz monitors but as a gamer they feel amazing!!! I describe the feeling as the same feeling you get from going form 30fps to 60fps in a game. I'm sure thats not true for everyone but that is the kind of feeling I got. Just butter smoother...*drowning in drool* Not sure how much of a gamer you are but you can even feel the difference moving the mouse around on your desktop.
I've read the same thing about the TN panel in the Asus ROG Swift. You could read my other post about what I think about TN panels and other panels. (or TL;DR. It doesn't matter much... to a point.)
While I'm excited for 4k its still relatively new to the consumer market and some stuff still needs to be ironed out, like new connection types, DPI scaling and graphics power plus I'd love to have high hz. 4k at 120+ hz.... that will take a while in GPU power alone.
Now with future proofing for a monitor I'm with you. I don't wanna spend a lot of money on something that will/might be out dated soon. The $800 is really steep and I'm a bit iffy on it myself but the thing is with 4K monitors now they will be shit compared to the ones that come out in a year. 4k is still new and a lot more changes will be coming to it and tweaking it to be better.
The pain of being an early adapter.
With DPI density you might just have to check out 2560x1440 in person to see what you think compared to 4k. For me I think I'll be happy a 1440p for a while.
I like high DPI and I think with my next monitor I'd rather have 120+ hz.
AND!! Thank you on being interested on my opinion