A soft opening will have no "schedule". It is essentially a chance for disney to let a ride or show go "live" w/ the public. However, if there are glitches it can be shut down for days or weeks to "tweak" the problem. This is because there is still plenty of time until the actual opening of the ride/show.
It just began it's soft openings, so you'll have a chance you may catch this show next week. The only thing is-- there is no set schedule for a soft opening.