First, the NYA agreement says nothing about dedicated hashpower. So any signatory can mine both chains, or neither, without being in violation.

Second, Core has already trumped the New York Agreement by releasing 0.15 which automatically blocks 2X nodes, even before November 1st. If the SegWit chain does not upgrade to 2X on Nov 1, the NYA is dead, and the miners will be completely free to migrate.

Third, your argument is somewhat nonsensical. "any big miner that wants to breach the NYA will not be trustworthy to its clients". What clients? Miners mine for bitcoins. Oh you mean wallets? The vast majority of Bitcoin users have no idea which miner full node their wallet connects to, much less how to change it.

"Third, you need to convince all users and shops to change software to support bcash payments." My article does not predict the victory of Bitcoin Cash. It predicts the possible collapse of the processing power of Bitcoin SegWit. If SegWit tranasction delays get longer and longer, while fees go higher and higher, nobody will have to convince anyone to use Bitcoin Cash. It will be the only alternative that works, which can be adopted at the least cost to businesses, because the protocol is effectively the same as original Bitcoin.