Wretchard at Belmont Club has an interesting analysis of China's plans and strategic concerns for the next couple of decades. He concludes that, despite its bluster, it is unlikely that China will launch an assault against Taiwan anytime soon.
The risk for China is not so much that the U.S. would intervene directly, but rather that we, or even the Taiwanese, would be able to block the flow of oil to China which would cause that country to collapse after about a month. China's oil reserves would last only thirty days - perhaps fifty days by 2010.
As long as China's access to oil depends on keeping a series of maritime chokepoints open the Chinese are vulnerable to the small Taiwanese submarine fleet. China's growing dependence upon imported oil, and the ease with which the Taiwanese could shut it off make, in Wretchard's opinion, an attack on Taiwan unlikely, at least in the near term.
Belmont Club's analysis makes a lot of sense, but read the whole thing and decide for yourself. Let's hope he's right.