First up, Guy, you should be happy with the latest rumor of a high Mp A mount:
(SR3) More tidbits about the Full Frame 45-46 megapixel (A-mount?) camera! | sonyalpharumors
We all agree this is the next move for DSLR and RX1 in Sony land.
Loxias - You have to remember these are very old designs - Planar and Biogon, and Zeiss are earning kudos for what they have done: a lot of modern niceties to bring manual focus lenses into the modern fold, with improved digitally-tuned performance, to use a bit of PR speak!
MTF has its challenges, but this site has side-by-side images of each Loxia and its predecessor ZM, both from wayback machine in Leica M days of yore:
자이스 Loxia는 ZM 대비 화질 개선이 미흡. BH포토에서는 예약 주문 진행 중 | DicaHub
fast translation: better everywhere. For corners and edges look at the lines above the bottom axis with numbers around 15 to 20. The Planar outer frame dive is no more! Its distortion is almost zero, and its image centre fine detail lines are now ultra!
Biogon (top set of graphs) is similar at f2, then *really delivers* at f5.6, esp at image centre where it is so good I want to see it against the RX1. Corners are overall better too, some astigmatism, these days well handled by design and glass matching. The final bugbear of M class lenses - severe light fall-off - is still around, being a design characteristic. Zeiss worry much less about vignetting, even in Distagons.
At Lloyd's site, *carefully focused corner sample* from the ZM shows just how bad things go when you insist on using film era huge beam angles (ray angle) in lenses, then put them on a modern digital sensor, and how well Zeiss did fixing the problem. Now we are back to where we should be - lenses being designed for cameras, not the other way around, as a fudge.
I doubt anyone will be very disappointed, after the brouhaha settles down and real shooters mount them eagerly on the a7 cameras. Good prices too, overall, for what you get. All just opinions.