The common thought amongst even reasonably educated and economically literate Americans is that China is 'stuck with US Treasuries' and has no choice, so it must perform within the status quo and do as the US wishes, or face a ruinous decline in their reserve holdings of US Treasuries.
I think China is already diversifying their reserve portfolio, and more stealthily and effectively than one would imagine.
Further, I suspect that through the use of hedging short positions and derivatives such as Credit Default Swaps, China would be able to cover a greater portion of its reserves than the common mind might allow. And if this is in reality one theater in a global struggle for power, sacrificing a pawn or two, and even a bishop, would be a small price to pay to bring down the world's remaining superpower, as indirectly and gracefully as is possible. War is never cheaply waged.