To be reserve currency Yuan doesn't need to be in peoples wallets. Reserve currency is about governments keeping significant quantities of currency as part of their foreign exchange reserves.
From Wikipedia:
 "People who live in a country that issues a reserve currency can purchase imports and borrow across borders more cheaply than people in other nations because they don't need to exchange their currency to do so."

But there is a question of Chinese government maintains capital controls on the conversion of its currency
Wikipedia source:
http://en.wikipedia.org/wiki/Reserve_currency#Chinese_yuan