It is hard to imagine how anybody could remain "Physically In - Mentally Out" of a religion such as the JWs, which demands everything from its rank-and-file membership. No difficulty, of course, being a "PIMO" member of any of the so-called "Mainstream Churches". In fact, most of their membership probably fits into that category i.e., get married in the church, get buried by the church, and attend a few church services in between times - but that is all.
Sustaining that same trick for any length of time with the JWs, though, would surely tear a person apart - mentally and emotionally? (I would have thought, anyway!)
As to the complete demise of the JW religion (whether with a whimper or with a bang), sadly not very likely. The more unpleasant forms of life are the ones which always seem to survive - even such catastrophic events as a nuclear explosion. For example, after a series of nuclear tests which were carried out in the 1950s on the then British territory of Christmas Island, it was noted that all other forms of life had been obliterated, except for the cockroaches and the rats. I rather fear that the JW religion is yet another unpleasant form of life which will somehow hang on, despite all the evidence on hand indicating otherwise.
PS: I hope I am wrong, but somehow don't think so!