And who will buy Chinese goods?
If West goes down also China goes down its that simple...
Chinese exports are 25% of GDP. This has come down from around 40% in the mid-2000s. As you can see China is reducing the impact of exports to it's overall GDP. As we speak the value of the increase in Chinese GDP is going up higher than the value of the increase in Chinese exports.
By 2030, China's GDP should be around the West combined. This amount of GDP concentrated in one country will propel it to natural hegemon just by the sheer amount of economic influence it will have all over the world.
The world is not static but dynamic. Otherwise one country will stay dominant for eternity.