As our friends pointed out I'm not an MF shooter. What I can say is that I have downloaded test samples for the P65+ from the Phase One site. Those images were shot by Peter Eastway, and I think shown a bridge in front of the opera in Sidney.
Anyway, the images had an awful lot
of lateral chroma but lens corrections removed them completely.
So I would say that lateral chroma could be a problem if it was not handled in software. Peter Eastway shot the same image on a Canon 1DsII or (1DsIII), the P65 image was much better. The Canon image was shot with a 17-40/4 zoom and also had a lot of lateral chroma, which also was handled by correction in the raw converter.
I would also add that when you go from say 25MP to 80MP the demand on the lens will be much higher. It can of course be argued that it is seldom more than 25 MP is needed, but I guess that a customer paying for 80MP also wants glass that delivers that resolution.
I include a screenshot of the P65+ image without and with lateral chroma reduction in LR4.2
As a small comment aside, fixed focals seldom have much distortion, except possibly very wide angles. Recently, Hasselblad relaxed some corrections on a few of their lenses so lateral chroma and distortion is handled in software. That may be reasonable approach, if they can use the lens surfaces to correct other issues that cannot be handled in software, like astigmatism and field curvature.
Is the latest version of high megapixel backs require more lens corrections?
I've used my Contax and p21+, p30+ for a long time and never used lens corrections. Admittedly, I don't shoot interiors or architecture so lining up walls is not that high on my list, but I do shoot into bright backlight, sidelight, fairly long exposures, mixed with flash and practical lighting and rarely, very, very rarely have ever seen any CA, or lens detraction.
In fact we just finished a project where we want more grit to the image so on the p30+ we shot at iso 400, which put me at F 16 for the majority of the shoot. I never saw any softness or detraction from those old zeiss lenses, in fact they are freaky sharp. If anything those old zeiss lenses are sometimes too sharp.
One thing I have noticed with my cameras is how much better the look of processing is in the last two years, with C-1 and the latest versions of Lightroom. Previously I thought the Phase backs were way too color sensitive and now it seems that skin tones are much more manageable and ambient color seems to pollute the image less.
Anyway, my point is, do the very high 50mp and 80mp cameras more sensitive in Focus, CA and detraction?