I suspect that BIIB has been solo for so long that it wouldn't want and doesn't need to merge.
Agreed that BIIB is doing fine and is unlikely to initiate M&A discussions; however, they might get an offer that’s too good to refuse. With Tecfidera as the flagship, BIIB has the kind of product portfolio that could attract a large suitor.
“The efficient-market hypothesis may be the foremost piece of B.S. ever promulgated in any area of human knowledge!”