Here is a 3840 × 2160 image, for reference. Ahem... http://www.upload.ee/image/1507311/miranda_kerr_2-wallpaper-3840x2160.jpg
I'll care when we have more content. Maybe that is in a year or maybe it takes 5+ years. But even then it won't be as big of an improvement as going from 720p->1080p which the majority of people can't even tell the difference from. So yes eventually it'll be an interesting very minor upgrade. Never worth buying a new TV for.
I agree with Draco. It's gonna be at least a few years before there is enough programing to even consider these TV's.