E-mount can be used with 36mm wide sensor.
But current lenses don't cover this size.
Do you have a source for the ability of the E-mount to properly cover the 42mm image circle needed by 36x24mm format? One issue is whether the diameter of the opening in the mount exceeds the 42mm diagonal of the 36x24mm frame by enough to let through the entire incoming light cones of lenses at minimum f-stop. For example, to support f/1.4 lenses, the diameter of the opening needs to be about
sensor diagonal size + (depth of mount)/1.4
so the minimum required diameter is about 14mm more for 36x24mm than the NEX sensors require (the sensor diagonals are about 42mm and 28mm respectively).
In other words, the question is whether Sony made the E-mount opening 14mm wider than is needed by NEX sensors.
Not that it matters much: it seems that new lenses would be needed for the larger format either way, and then even if the mount is different, those new lenses could easily be made usable on NEX bodies via a full-function adaptor.