Actually, it's widely believed by many (especially in the u.S. government) that the RMB (CNY) is artificially undervalued and kept "weak". The Chinese government likes to keep it that way because 1) it keeps Chinese exports competitive and 2) China would taker a bath on its $2 trillion foreign reserve (a significant amount in U.S. treasuries) hence China's wish to move away from holding USD.

The day you see China largely abandons holding the USD in its foreign reserve is the day the USD is worth as much as the pre-Austral Argentinean Peso (i.e., not much), especially if the U.S. loses control of its fiscal situation.