I agree, the sooner World War 3 happens, the more likely an American victory will be. But an American win isn't very likely even now, as China has an enormous advantage: that of being the defender. The US would have to be two or three times stronger than the Middle Kingdom to be reasonably sure of winning; that is not the case even now, and the advantage can only tilt more in China's favor 5-10 years from now.
But in 10 year's time, it should still be favourable for China to wait another 10 years as it continues to grow bigger.
China can aim to be 2x and then 3x bigger than the US.