Indoor coasters are never that long. For example, the WDW Space Mountain tracks are about 3200 feet and RnRC is 3400 feet. The longest indoor coaster in the world is about 3800 feet. Based on Disney's comments this will be one of the longest, I expect it will fall between 3400 and 3800. If you aren't making long straight tracks and drops, never a hallmark of indoor coasters, you can fit a whole lot of track in a space as large as that building. There are 2 3200 foot tracks in Space Mountain. I doubt there will be double tracks in this building.