If 90% or more of the miners supports it then its really core who should add replay protection and change the difficulty adjusting.
Why are we still disusing this?
https://blockchain.info/en/poolsF2pool is %10+ of the hashrate, F2pool is not support segwit2xCoin anymore. Reason they are still voting "intentional" and noobs think it's still relevant:
https://twitter.com/f2pool_wangchun/status/906022864389681153So thats -12% ish hashrate support for 2xCoin, and that doesn't count Slush and other miners that will defect.
The legacy chain will not disappear. Bitcoin will not lose.
I think you are overestimating the power that some pool operators have. Even if the owner of
F2Pool decides to not support Segwit2x, it is entirely possible that the hashers (=the people,
who actually mine for F2Pool) have different preferences.
Besides, I don´t think that mining pools will be the decisive factor. It is more probable that
the miners will switch to the winning side - irrespective of which chain actually wins out.
The outcome is more dependent on the decision, which chain gets the desired "BTC" ticker
symbol at the main exchanges. As far as I know only Bitfinex has already clarified their stance
on this question. The other exchanges still haven´t addressed the upcoming fork.