China will be a fellow superpower, they practacally are now, but things depend greatly on how things change within The Party, and how they respond to the changing pressures as people want an increasingly democratic system, demand civil rights, and the other pressures as china advances.
They could easily erupt into a bloody civil war years from now if the old guard refuses to sede power, which would pretty well crack their plans on a global scale.
By the same tolken they could simply ride the wave...
You also have to take into account china's military inexperience, the current generation of chinese soldiers and commanders have never seen conflict against an equal power, shooting tebetian monks or putting down dissidents makes poor practice. Whereas the US has been doing wars and peacekeeping, albiet more than we should have.
Moreover both sides have a good reckoning of each other's abilities, stratigy, and tactics.
Chinese commanders have studied US/Western tactics on paper and in simulated battles, it's one thing to say "okay, we know what they can do, we can take them..." and an entirely other thing to actually wage a war against a foe that is far more experienced than yourself.
I'm not saying war would be a good thing, nor that "we'd win cuz we're americans by golly" i'm just saying should a scermish erupt it would be a pretty even fight.
Besides both sides would loose economically, we are co-dependent especally in this international market. If we crash, they crash. If they crash, we crash.
On their side of things imagine hundreds of millions of tons of products just rotting on the docks. while nearby markets might see a surplus in chinese goods, the US buys about half of all goods prodouced in china. So their unemployment would skyrocket, and many fortunes would dissapear overnight.