once there is trust on crypto and it is accepted mainstream most countries and their central banks would fall in line

it is a possibility but it is a long way from happening. massive adoption needs to happen and bitcoin should be less and less volatile over a long period . that way trust for bitcoin would increase and more and more  and people would embrace it, hence dependence on fiat would reduce

A good idea to influence e-commerce websites to accept bitcoin as a payment option. i think a stumbling block would be crypto is too volatile for now to be used as payment by these sites.

I agree with this post even though mainstream usage doesnt only depend on the users.