The U.S. empire is headed for a cliff. Maybe it will even collapse within our lifetimes. But that collapse likely won't be the end of capitalism as a system; it has survived the collapse/diminishing of other hegemonic powers before. But what would the next hegemonic power even be? The EU? Russia? Japan?
I want to believe that the U.S. is the last stop on Mr. Capital's Wild Ride, but that seems naive.
I'm not necessarily saying China will push it's ideology on other countries, but if they get to rewrite the rules of the international economy, they can potentially do so in ways that are more favorable to the socialist- or at least state led, publicly owned- mode of development. This is why you see so much fearmongering about them pushing their "authoritarian" system internationally when they become a peer of the US.