Here's why it'll be hard for the yuan to replace the dollar even in the next 20 years, according Stanford historian Niall Ferguson

• China's yuan is unlikely to replace the US dollar within the next 20 years, according to Niall Ferguson.
• The Stanford historian pointed to several challenges China has in displacing the greenback.
• Still, he acknowledged there were risks facing the dollar amid shifting trade dynamics. 

China's yuan is going to have a difficult time replacing the US dollar as the world's supreme reserve currency – and it's likely not happening even in the next 20 years, according to Stanford historian Niall Ferguson.