I'll bet it never happens. In fact, I hope it never happens.
I never saw the musical, and have heard that I really missed out, but I couldn't get past how stupid the premise sounded.
I don't mind the idea of a sequel, let those who enjoyed the first one see it. However, I do mind because Brian and Roger won't just let others handle it. They would almost certainly take their precious time and screw around with it.
I know I am being selfish, but I want those two put under house arrest with ankle bracelets not allowing them to leave the record studio. For good behaviour, like releasing an album, they can be let out to tour, but that's it.
Seriously, I hope it's at least a long ways off if it happens, but I doubt it will.