We hoped that early May would be the latest that SAE would be published by. A few stages of development slowed this down, including a mismatch between the provided form and the behavior of the add-on. Google actually published it, but a quick check demonstrated a problem existed. In addition, settings in OAuth–this relates to the end user approving account access to the Add-on–were not correct.
The OAuth has been resubmitted, so as soon as it it approved, so as soon as we are cleared we should be able to make SAE available for public use. We expect Monday May 7, but time will tell.