Night of Joy will not be returning to Walt Disney World in 2018. In what has seemed like a slow death march, the event moved away from Magic Kingdom and to ESPN Wide World of Sports in 2016 and then experienced very low crowds and even a cancellation of the last day of the 2017 event due to Hurricane Irma.
According to internal calendars and sources, the event will not be returning in 2018. Additionally, the 13-time Night of Joy performers MercyMe will be at the Eat to the Beat Concert Series at the Epcot Food & Wine Festival instead. Disney has also permanently removed the Night of Joy page from their website.
Disney has not made an official announcement about the event yet, so this should still be treated as a rumor until such an announcement.