I feel like they may have chosen Rudd for just this very reason- he's an affable host who goes along with anything, and doesn't mind sharing focus with other guest stars, cameos, etc.
His first time hosting, Beyonce was the MG and there was all the attention that the "Single Ladies" dancers sketch got. His second time the MG was Paul McCartney. Last time he hosted it was One Direction, plus there was also the big "Anchorman" reunion when they did the Bill Brasky sketch at the end of the show.
So I'm figuring it being Kenan's last show, combined with DJ Khaled as the MG , means we're bound to get lots of cameos, other musicians appearing, probably a big final blow-out "What's Up With That" sketch, etc.