Just my opinions.....
If you (or I) are serious about landscape photography image quality right now then we should go out and buy a Nikon D800. Simple.
In terms of image quality the D800 far exceeds all other current DSLR cameras, it matches the quality of some digital medium format backs and surpasses most medium format digital cameras. Add to that Nikons brilliant glass and you won't need any more resolution or image quality for any application.
I cannot afford to sell up with Canon and move to Nikon and although I have considered it many times in the past and now, in light of the D800, seriously considered it, I won't. Mainly the reason