The Grand Opening is April 7th... But, the Grand opening is when they do the press events and "officially" open the attractions. Attractions go through a soft opening prior to the official opening, so it will probably be open on a regular basis sometime in Feb or March. Soft openings are a test and adjust phase where they may be open or they may be closed, they could open for a few hours in the day but it would be un advertised, this way they can shut down to work out any kinks or tweek things as needed. The DVC/AP previews are January 26-29 so I would expect soft openings to begin shortly after that.