New Metabones Booster and NEX-7 Magenta Edges
IIRC magenta corners are mostly a problem with e-mount and rangefinder lenses - ones designed for a short flange distance.
Metabones is apparently not planning on doing one of these adapters for Leica rangefinder lenses, as there is not enough room to squeeze in the extra element. This adapter is only feasible for SLR lenses which get mounted farther out.
Since the adapter glass would occupy a space closer to the sensor, it might project to the corners at a steeper angle and thus be prone to color casting.
I will be very curious to see some sample images once they become available.