A source was that kind to explain me the different solution Sony engineers found to create the hybrid A an E mount camera. He didn’t unveil to me which one has been picked up by Sony. But here they are:
a) Singular mount that accepts all current lenses at differing distances from the sensor plane.
b) Sensor that moves the focal plane inward and outward dependent upon the mounting of all current lenses.
c) Singular mount that moves all current lenses at differing distances from the sensor plane.
d) 3 Interior (in-body) camera mounts that can be user switched dependent upon the mounting of all current lenses.
e) Redesign of all current production lenses to one physical mount.
That said I don’t know if it makes really sense to work on those kind of tech solution. I think it makes mroe sense to keep the E and A mount system separated.