"Many of the establishment have clearly bought into this idea and now resistance to the idea has emerged. I believe how this will go in the long term will depend upon how the establishment react to this resistance."
I'm not sure they actually have bought into it.
IMO what has happened is that the TRAs have very cleverly insinuated themselves into grassroots politics. It's easily done, takes very few people as so few of us are active in politics. From here they spread the TWAW mantra, others don't want to disagree and be called nasty names so they go along. Uncontested TWAW are all the elected hear from their constituency bods. They give it no thought and parrot what they hear, assuming their people have done their homework. Which they haven't. They don't think about it, consider it a minor point affecting only TW, who they consider to be a vanishingly small number of people therefore SelfID is fine.
By not thinking about it they do not consider that it is so badly defined that it will be open to abuse by predators. When it is pointed out, they're still not giving it any headspace and pooh-pooh this as bigotry.
But - eventually, alternatives to TWAW will filter in. And they will have to give it headspace. Some will cling on to it, trying to save face as they think they can't afford to 'do a U-turn'. (I'm looking at you, Maria Miller.) Others with more integrity will start to use their eyes, and it will depend how diligent they are, how much time they can spend looking at it, and who's still dripping the mantra into their ear.
So yes, I agree with you OP that "how this will go in the long term will depend upon how the establishment react to this resistance." And I do believe that eventually, sense will prevail. But so, so much damage will have been wrought by then
.