new landscape lens for new D4/D800

Good evening all you late night shoppers!

I hope to very soon change from my D2Xs (DX) camera to a D4/D800 (FX)

I have the D2Xs and have really grown to love shooting landscape over the past few years.

I saw a photographer at local art show who took the most detailed photos of landscapes with real depth by leaving the lens open for a very long time using a very small aperture (he also had ND filters in front).

So, the only lens that I have now with a filter at this time which is wide angle is my 24 - 70 but I feel that I may wish to go wider.

What lens would you suggest that I get?

Prime or telephoto?

eternal camper