Im currently looking to upgrade and considered D750/800/810. It all comes down to budget at the end of the day but I plan on hanging it out until I can afford the D810. The way I see it the 800 although an amazing camera is some years old now which suffered from a few niggles and was let down by frame rate, ISO capabilities and auto-focusing.
For me upgrading from a D7000 im sure I wouldn't even notice these things and it would offer a staggering upgrade, but id rather stretch myself to buy the best I can to future proof the investment. If I opt for the 810 which was released early 2015 it will see me good for 6+ years where as the D800 is nearly 4 years old now.
don't get me wrong if I would be MORE than chuffed to own an 800, but as I said if I buy bodies to last a long time. My D7000 is 4.5-5yrs old now and if I wasn't changing to FX would be more than happy to stick with it.