Cro's link was to a page full of articles, the only one of which I could find that would relate to this thread was about China's policy to back "outbound investments," which basically means they should continue buying foreign resource properties like oil wells and various mines, although of course it wouldn't be limited to that, it could be anything from IT to hotels. Not necessarily buying dollar-denominated properties either. Depending in part on political considerations.
As far as them dumping T-bills, it sounds like cutting your nose to spite your face. They couldn't dump the whole hoard all at once, and if the first dump had any significant effect on the dollar, it would simultaneously devalue all of China's remaining T-bill holdings, plus most major currencies would probably be lifted as the dollar fell, so their reinvestment of the proceeds of their first T-bill sale would also be buggered up. They are doing very well with current economic policies and in addition to their export markets have a vast internal market to satisfy. They are basically faced with the problems all industrially developing nations have faced, shortages of raw materials, which used to be solved by imperialism and now need a more modern form of the solution, economic imperialism and neo-colonialism. For which they will definitely need to continue developing their military muscle, much as they are already doing.