Awesome. 4k Televisions and programing are rolling out much faster than the transition to HD. A very compelling reason to get Amazon Prime if you don't have it already wouldn't you say?

4k is still to expensive for me

It's still too expensive for most people, and will be for a few years. I'm happy with 1080P, in fact I just got a new 42 inch LG 3D TV, it'll most likely be out of date by the time 4K comes into it's own. Remember too, 4K is going to suck down a TON of bandwidth, that will wreck havok with most people's home broadband connections and their caps, forget it on mobile with their puny caps and often overloaded networks.  

On the "we're at the very beginning of a mainstream transition from Full HD 1080p (1920x1080) to 4K Ultra HD (3840x2160, or 8.3 million pixels" thing, 99% of broadcast tv maxes at 1080i, first we need to get that to 1080P, then work on the 4K thing. 

MCook; 4k isn't actually that expensive and it won't take years to drop in price. Smaller and lesser known brands are already selling 4k TV's at or right above mainstream HD TV's and something like this at Amazon insures you at least some 4k content for no extra cost (provided you have amazon prime). HD Tv's started at much higher prices and took much longer to hit mainstream price points and not only was 1080i content hard to find but 1080p didn't exist especially when it came to broadcast programming. I am guessing that anyone looking to buy a TV in 12-24 months is going to seriously consider a 4k tv and won't want to settle for HD TV's anymore. 

As for your 1080p argument why would anyone focus on 1080p broadcast when you can leapfrog it and move straight to 4k? 4ki would still look a hell of a lot better than 1080p. Also there is some 1080p content out there, for instance Dish Network offers 1080p for on demand movies I believe.