May be, may be not. May depend on what you are doing.
The Nikon D800 has a big resolution advantage, not even the best lenses would compensate for that.
On the other hand, Leica makes a big effort to make their lenses performing well at large apertures. Stopping down eliminates the resolution/contrast advantage of the Leica lenses, most lenses are pretty close at f/8 or so. You know, diffraction, laws of physics.
Third, there has been much development in optics recently. I have seen a couple of publication claiming that the three Sigma macro lenses match any lens made by Leica, for instance.
By the way, once you are past good enough being best may matter little. Can you see any advantage in a correctly made double blind test? If not, does it matter?
DxO-mark is not related to lens, by the way.
My take is that the Leica got much more useful. I'm not sure about the significance of DR, but it seems that the new CMOS sensor is a major step up in image quality and high ISO capability.
True, since the 80s, they have always been lagging behind the Nikon-Canons.
But I would dare to argue that the Leica glass compensates for a lot.
So, looking forward to try my Summicrons on this new sensor.