Good article about something the few discuss. Russia and China are currently making nice, but have many issues between them (chiefly the lands that Russia stole from historic China).

1) As you say, invading Taiwan would be costly (plus shipping lanes to Shanghai would be disrupted, hurting China's economy). The West has several levers (including naval blockade and powerful alliances). China must be wondering if it would be worthwhile.

2) On the other hand, if Russia falters in its Ukraine invasion, look out! The recent ISIS terrorism is an indication that the "Stans" want to be free of Russian hegemony (and probably want more land). China wants to take back what they feel is rightfully theirs (Outer Manchuria). As you say, mineral rich and relatively easy to take.

3) I've always thought either Russia or China would come running back to the West. They have too much to lose without us. The question might be "would the West prefer to make nice with China or Russia?" Culturally, you could almost see Russia being a NATO ally someday (but foolishly they think they can take over the world, take Alaska back, etc). Siding with China (more powerful) might increase instability in Eastern Europe, plus we wouldn't want to ignore China's human rights and hegemonistic violations. The West should be neutral, I would think.

4) A rise of united "Stan" countries might have us all worried.

5) With global warming, Siberia may become prime real estate...its happened before!