How long till the next?
Stay on the watch for something else...
An artist, in whatever field, cannot produce their best work to a predetermined timetable.
Similarly, the a= series, being governed by artistic principles, will not be produced to a prescribed timetable. As a new a= design emerges so will notification of its progress, to give a 'heads-up to those who may wish to become its new owner.
Currently, there are only two completed designs in the a= series.