As Greg has already said, the Z1 doesn't have 4K nor will it ever get it I don't think. As for 2K, it's probably more plausible to get that than 4K, but again I can't see it happening.
In all fairness you aren't missing out on that much, at the end of the day it's simply a phone and for the most part you're showing other people what videos you have on your phone / tablet / computer.
If you really want 4K video then a phone that supports it out of the box is where you want to be.
Not great news but hey ho.
Phones: Moto 888 - Nokia 6110 - Nokia 3210 - Nokia 3310 - Nokia 8210 - Samsung e250 - Sony F305 - LG Viewty - G1 - HTC Hero - HTC Desire HD - HTC Sensation - Nokia Lumia 800 - HTC EVO 3D - Samsung i9300 - Asus Prime TF201 silver - HTC One - Galaxy Camera - Z1 - Galaxy S5