There actually is 4k content available now, infact it is easier to make your own with the $5000 USD JVC handheld 4K camcorder..... Saying there is not any 4k content out there now is not true. Commercially there may not be much though.
I am soooo excited about 4K and how quickly the price is dropping. 55" is about the smallest you want to go for your average living room (any smaller and there is very little difference between 4K and 1080p), but I am holding out hope for a 40-45" 4K display for use as an oversized computer monitor. First company to do such a display that can hit 60Hz and treat the whole screen as a single display for ~$1000 will get my business.
I may have to wait a bit before this happens, but considering how quickly the prices have dropped since their introduction last November, I can't imagine that it will take more than a few years. I'll have to wait a few years before single GPUs can properly drive 4K displays above 30fps anyways, so I suppose I can sit back and wait patiently.
That is actually a pretty decent price. Personally I prefer a bigger screen, but not until I can get a 65-70" for around $2500. So hopefully in another couple of years, assuming that enough content is available for it to be worth the investment.
Allso you can upscale your 1080p content to 4K, just like you can convert normal dvd to 1080p resolution. It is not perfect, but in most cases better than looking native 480i or 576i used in DVD movies! (compare it like playing a games with PC with or without anti-aliasing)