As individual entities, perhaps. As a bloc? NATO member countries total population is about 800 million, if I'm not mistaken. The Western world is hardly going to disappear.
And of course the US, unlike China, has immigration as its foundation. They could accept, say, 20 million educated and/or wealthy immigrants from China over the next 20 years, with no shortage of takers ( http://news.ycombinator.com/item?id=2660178 ), which would strengthen America and weaken China.
The current major issue with SCO though is it needs either India or Pakistan or both as its members to make it a formidable military alliance. But since India and Pakistan are archrivals there are differences between Russia, which has always backed India, and China, which has always backed Pakistan.
[1] http://en.wikipedia.org/wiki/Shanghai_Cooperation_Organisati...
This is true. In the long term, Russia needs to decide whether it wants to be a satellite of China, or part of NATO / the West.
Bear in mind that SCO isn't actually a military alliance (with mutual defence obligations) yet, although it may become so in the future.
This is the best way to weaken China. In fact, it's the best way to weaken any poor country. Just pay the best people they have to come to your country and become permanent citizens. It's still not too late. Within 20-25 years, there may be no advantage for them, but right now, there is still something for the Chinese to gain by moving here.