They will try, and they will most likely succeed without much issue. They'll do scare tactics first to get buy-in from the public, like they do with everything else.

Sure, fork BTC, and then see how that works out when everyone that actually controls mainstream bitcoin usage (banks, investors, payment processors that retailers use, etc.) only support the mainline fork.

How much does BCH matter anymore? It will be the same. Yes, fringe people will use it, but you won't be able to participate in the mainstream economy with it.