Where are you buying TVs? The 40UB8000 is currently being liquidated all over, you can actually find it under $600. I suspect that by next December that almost all TVs will be 4K, It's more expensive to make a 4K screen that's 15" but for a 50" screen it's pretty easy. The pixel density is lower than a lot of 1080 laptop screens.
I'm waiting for a 45"-50" 4K IPS from a decent manufacturer (Like LG, Samsung, Sony or Sharp) for less than $1000. Now that's the sort of screen I want to have for the next 10 years. I figure I'll be able to pick one up within a year. Heck LG might announce it at CES and I'll pick it up just before they announce the next model in December 2015. The TV makers seem to be falling over each other to offer huge sets at low prices.