I see five different options for the days leading up to the opening of Pixar Pier (Incredicoaster):
1. A hard ticket event the night before the opening (like they did for GotG).
2. A media preview the day before (like they did for Pixar Fest)
3. An AP-only preview day
4. An unannounced soft opening
5. Nothing
Those are kind of in the order that I think are likely...it would be nice if they did a soft opening to work out the kinks, but as Hydroguy said, this is basically just a re-theming so they might not need much in the way of a soft-opening. Keep an eye on the Parks Blog as we get closer to the re-opening. They'll announce in advance if there is going to be a hard ticket or AP-only event beforehand. They probably won't announce anything for a media preview or a true soft opening.