I believe it was 'staged' in as much as it was a filmed performance, carefully scripted, (in spite of it cleverly appearing to the contrary), probably with certain carefully positioned 'fans' (actors - at the front, I'm thinking of one over exuberant gentleman in particular!) to convey the scene of a much loved and missed entertainer announcing an exciting final project to his adoring audience (to make what will happen next, which is in fact the main event, even more shocking and poignant).
But 'staged' as in green screen? No, I think it really happened.
To go back to Thriller's first post, it is odd for that split second shot (Thriller's screencap) to be included in TII. Why? Does it add in any way to the O2 segment of TII? Don't think so, as it's too quick to even be noticed by most! Thriller, were you going through the film frame by frame to even find it?!