1) If you look at how hard even multiple GPU (SLI, Crossfire) top end cards struggle with today's maximum resolution of 2560x1600, or a three-way 1920x1080 setup (effective 5720x3240) in a game like Crysis 3 with all the eye candy maxed out, you will see that 4k resolution for PC gaming (or console gaming) is a long, VERY long way off.
2) I remember seeing my first HDTV on display at the Smithsonian Technology Institute in Washington DC back in 1994. It was running 720p resolution, and I believe it was a Sony. They were showing a soccer game and I'll never forget actually being able to see the audience faces for the first time. It truly was like looking through a window. But what you have after 720p resolution is a law of diminishing returns. Think about it: 1080p does not look *that* much better than 720p from a distance. It's because the human eye can only process so much information, similar to why we can't tell the difference between 60fps and 120fps, but we can tell the difference between 15fps and 30fps. With 4k, sure, it looks better, but not blow-your-mind better.