It is not sure that China will ever overtake the U.S. economy. If it does it still will be a very poor state. If you devide their GDP per number of their citizens (1.3 billion) it will show you the real weakness and condition of their economy. Check out this article:

http://www.europeancourier.org/China_06_10_2006.htm

I believe the going prediction among scholars is around 2040 China will overtake the US. They are still far behind, but it is obvious that the Chinese middle-class is growing by the fact car sales are on the rise.

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"The person who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself. " — John Stuart Mill

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"The heart of the wise inclines to the right, but the heart of the fool to the left."
Ecclesiastes 10:2 (NIV)

only if they think we'll sit and watch...
Of course given the way we act toward China these days, why would they believe otherwise?

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"Man lives in the sunlit world of that which he believes to be reality. But unseen by most is an underworld, a place that is just as real... but not as brightly lit... A DARK SIDE!"
-opening from Tales From the Darkside

In my opinion conflict over Taiwan is presently very unlikely. The Chinese economy is growing but even if it overtakes the U.S. economy it would take them another decades to match the military power of the U.S. And still the technology advancement distance between China and the U.S. is enormous and this is what would matter the most in the potential war.

There was a very interesting article recently, I think it was in Foreign Affairs, about the U.S. nuclear weapons and Russian strategic nuclear weapons. The conclusion was that presently the U.S. would be able to completely destroy Russia and its strategic nuclear weapons with one strike, which means that there would not be any response and danger of nuclear counter-attack to the U.S.

If China wanted to start war over Taiwan it would firstly have to not only possess comparable nuclear arsenal but would have to exceed it to the point that it would be able to destroy the U.S. and its strategic nuclear arsenal with one, preventable military strike.

In my opinion China could presently risk a conflict over Taiwan in two situations. First one is, if the U.S. would be attacked with nuclear weapons by terrorists and the rapid falldown of its economy would follow and the public, government would be focused on different issuses and would not be willing to risk a conflict with China over Taiwan. The second one is if the U.S. would be military engaged in too many war theaters at the same time. For example, Iraq, Iran and possibly North Korea. Then another conflict would be too much economically and military.

China is building up Offensive weapons that are first class and american Military equipment is ageing. And there Anti-seccesion law basicly says they can invade taiwan when ever they want. In the event of war china is more then a match for the United States.

This whouldnt be possible americas attack whould be detected and then a couter attack whould be launched before the nuclear weapons were destroyed.

They whouldnt have to nuke the united states, there is no way America whould start a nuclear war and no reason the chinnese whould do it. they could invade taiwan and south korea bomb japan and still have forces attack any naval response. Also they Cyberoptic warfare units are the most advanced in the world. They could shut down the worlds economy fairly quick.