The WT won't go out with a bang. It will go out with a whimper, slowly declining and shrinking. Somewhere along the way there will be a "come to Jesus" moment (pun intended), and the entire 1914/607/adventist root will be discarded. At that point the WT will be a bland Christian sect, no different than your local Baptist church, with a somewhat (but not much) larger membership, scattered about. Heck, probably people will me members of JWs and the local church.
It will remain small, only gaining members among the truly religious.
Probably won't happen in my lifetime. Maybe my kids.