According to an interview with Don, Glenn will be doing a stint on Broadway! Sally of Rockphiles did some research and discovered it is probably the musical Chicago, and the role is probably Billy Flynn.
BTW, does anyone else think that Don sounds a pit pissed off at Glenn in this interview? There's several "I didn't want to do this but I was overruled by Glenn" type comments. Hopefully they will continue to work together in the future at some point despite the tensions (ie TOUR).