Personally I am dreading 4K right now. I think it's too early to change standard already. Yes I am aware how much higher quality it is.
Why I don't like it... first, there is a huge problem with content availability. There are hundreds of thousands of movies that still have not made it to 720 or 1080, but for that matter there are loads that were never even released on dvd either (some of the best 80's trash sci-fi / horror will be lost to younger generations forever as it has not been released since VHS/LD a real shame). Now think about how poor 480 content looks like on 1080 display, now think about it on 4K it becomes the size of a postage stamp and when you full screen it I can't even image how awful that will be. 720 becomes as bad as 480 is now, and 1080 will only be marginally better. I mean, I don't even buy movies at all and I am still annoyed with this.
Next we come to PC use, gpu are not powerful enough to drive that high res for gaming at any reasonable quality level with a good frame rate. You would need power of like quad sli 680 to even attempt it for something demanding.