Of course, at some point, there will be enough MTF in a camera body to cause the lens to be the limiting factor, but that is well out in the future, we are not near reaching it.
I wouldn't necessarily say that. Go read about the lengths D800E users have to go to in order to get all the resolution out of their sensors. You have to use the _very_ best glass and hit the perfect f/stop with the perfect focusing (hyperfocal generally). It is already getting quite fiddly to feed 36mp... if Canon is going to do 46mp things are definitely going to get interesting.
BTW - It's a pet peeve of mine that many "landscape photographers" don't truly understand diffraction, DOF and hyperfocal focusing. If you think "all landscape shots are at f/8 or smaller" then you need to go do some reading and shooting.
Just go get a really good camera and lens, stick it on a good tripod, use manual focusing and mirror lockup and go through a series of shots from f/4 to f/22. Choose a good landscape scene with foreground interest (although your camera doesn't have to be right up against the foreground interest) and go through the aperture series while focusing at 3 different points:
1. At the foreground interest
2. Halfway to the distant object (like mountains or a far off building)
3. At the distant object
Compare your results.
The results will be pretty damn obvious. You'll get the best sharpness focusing halfway between (which is just an approximation of the hyperfocal distance that will be good enough for you to see what's going on) the near and far subjects and with an aperture that is just on the large side of the diffraction limit (generally around f/5 to f/8 for most modern sensors and good glass).
By focusing better (right at the true hyperfocal distance) you can get everything sharp with larger apertures (I'm using f/5.6 more and more often lately in my own work).
If you use a tilt-shift you can do even better than that because you tilt the focal plane so that it more closely approximates your scene (instead of just being perpendicular to your lens).
All of this is a way of saying that as we get higher MP sensors... we (the landscapers) are going to need to do more work and be more diligent to get the very best possible image.
I read an article not too long ago where a pro (really?) landscape photographer was advocating shooting everything at f/22 focused at infinity. I nearly lost my lunch. How could a "pro" never have even done the above testing? Because when you're using film or only 10mp it simply doesn't matter that much....