D800 do provide as it is one of flagship from nikon,
but do you really need those megapixel?
do you print out all of your snapped pictures or share it digitally?

since you do mention you focus your work vastly with landscape and i believe af would be the least of your worries.

like what others keep pointing out, body changes lens is here to stay.
with Nikon 14-24mm f/2.8G to play around and compared to a solely 50mm.

I think the choice is obvious.