A bit of this gets into the weird apples and oranges thing....
Traditonally (at least as I understand it) lens resolution was measured by how many lines per mm could be resolved on film.
But digital doesn't use film. It uses little dots.
Now, from what I understand, there is an absolute limit on len resolution due to physics. You simply won't be able to resolve past a certain point.
Now here is where I see it getting tricky.
Say you "hit the wall" resolution wise and have a CCD that is say twice as good as the lens. In other words each pixel is 1/2 the width of the smallest resovable line.
You just market it. Nobody can really tell the difference right? I mean sure only 1/2 the pixels will be "used" (o.k. will be needed....), but why stop there?