... so your answer to the OP's question is ?
That on a 6D the Nyquist limit is about 78 LP/mm for a monochromatic grayscale subject, and 39 LP/mm is where its at for absolute full colour resolution. I would not want to pass much more than 55 LP/mm to the sensor of the 6D. I am sure that the maximum resolution of the original 24-70 f/2.9 L is going to be plenty enough for the 6D sensor. Actually I think the max resolution of the lens will be perfectly adequate on the 7DII or 5DS, or even the new Canon 24 MP APS-C sensors. My previous post being the reason why!