to exchange Taiwan for Iran?

Were it to do so, it would resemble what Nixon did with China in the 70's - to reconcile/ally with China in order to defend against Russia globally, and to withdraw its military force from Vietnam properly to comfort US people.

Once again, the price, which US will pay, is Taiwan. Inevitably, Taiwan, as a little chessman, will be abandoned by US again. Otherwise US will never win the war of Iraq; or in another word, US will never dominate the oil in the middle east.

However, the oil is the blood of modern industry, which both US and China needs desperately in order to expand their economy. I personally don't see that in any near future Taiwan has the capacity to declare independence officially. Or, in short, Taiwan will be united by mainland China.

If China allows US successfully to conquer Iran to control the oil supply in that region, China economy may not confront serious challenge, and it will not expand at the same pace as it did in the past 10 years. It's a dilemma for Chinese elites in Beijing.