To follow on form @Kernow 's point, i think that a limitation on the power output, and actually not a speed limit is the key issue, and that actually using speed as the distinguishing factor is the wrong metric.
I would quite happily ride a lower powered motor with no limit, versus a higher powered motor with a limit.
It seems to me that the bikes should be classified on power rather than speed.
I agree that there does need to be classifications in place to protect out trail access etc etc, its just that speed is not the right way to do it.
But at the moment 250W continuous power and the 15mph assist speed limit together are the classification requirements. Personally, I don't see it changing for the better in the foreseeable future and if the trail access is someone's concern then disabling the assist limit is working completely against it.
Just as a side note, most of the systems are cutting off nicely @15mph. Even Shimano with the 4.5.1 firmware improved a lot and in Trail mode, the assist cut off is barely noticeable.