Starting in 2016, Disney’s Night of Joy is moving to the ESPN Wide World of Sports Complex. All of the concerts will occur at the complex and there will be dedicated bus service to take guests back and forth to the Magic Kingdom.
The Magic Kingdom will still be limited to those that have Night of Joy tickets, but because of the move they will be able to sell even more tickets to the event. I am not sure what that will do to the crowd levels for the attractions.
ESPN Wide World of Sports Complex does have indoor stages, so that will make for a great musical experience regardless of weather.