The short answer is no one knows. The longer answer is never, I've never been to WDW (been going for close to 40 years) when there haven't been construction walls somewhere. They are always either improving, repairing or changing something. Because they chose to do a major overhaul smack dab in the middle of Epcot, it made it a little more noticeable then normally when they are just doing a ride or a building. I've been a number of times since the walls have gone up and to be honest, I don't even pay attention to them any more. I don't think anyone is even 100% sure what the Moana area is actually going to be like. Are you going to be able to cut through it to other places in the park or are you going to have to walk around it? Who knows.