Zeiss maybe gambled a little that, instead of making a new design, they could improve on the ZMs enough to get past the quite typical midfield curvature so many near normal M lenses have. The irony is the Planar 50/2 ZM is very good in this respect until the far corners, albeit at lower contrast.
Overall, they did very well, boosted contrast stopped down but (always a but) you do get a fall in midfield (IH 15mm). This is where the DSLR mag charts are misleading, as contrast rises in the corners of the Loxia. Something has to give. Even the ZM 35/1.4 has a little residual midfield curvature but it's already at such a high level no one will notice!
They (Zeiss) admit contrast in the L50/2 will be lower up to f4 compared to the FE55. 50mm lenses are a kind of cross over point - people want great bokeh and strong centers but these days the images get closely peeped, so smooth outer frames and good corners are needed too. People will likely warm to the Loxia images over time, and they really dress up the bodies.
I don't reckon there is much room for Sigma in FE, with CZ and Sony hard at it.
'I miss a high quality 85 mm lens for the FE mount'
Let's start a petition!