If you are satisfied with your F8000 , I say "keep it" !
Here is why :
4K broadcasting , many years away , sure you might have heard just around the corner , but it is not.
4K Blue-Ray , yes that is happening , along with the PS4 , and it too will be 4K ready
Still , broadcast is the key to a winning format , look at BD`s and the way broadcasters scrambled to Hi Def
They just did that yesterday , in broadcast buying terms , so they will not be doing 4K any time soon.
Save some coin , rainy days ( and snowy ones) may lay in wait .
I used to be an early adopter , had the LD`s and the AC3-LD`s , but all long gone , money wasted
If the F8000 is letting you get a good nights sleep , keep it and be grateful you have a good one !
Best of luck