Disney hasn't been very definitive other than "Spring 2016" (which, in theme park speak,?can really mean anytime before the end of June). The date I've month floated around is April, but like WEDWDW indicated, construction on the seating area is going slower than expected, so that could get pushed back to May. My understanding is that most of the show elements themselves are near completion, so I suppose soft openings could occur before then should the seating area construction pick up pace. They also need to run trial shows to allow the animals to get used to the shows as they'll apparently be noise bleed in some of the animal areas.
And yeah, this show is going to be incredible. I've heard it described as World of Color meets Fantasmic!, which sounds massive. And Disney is expecting this to be big. Like WED said, two to three shows per night will be the average, and they're considering using the Discovery Island trails as a holding area for the next show during the current one.