i think it cannot happen, because bitcoins is a digital amount, while money was a daily currency needs in exchange of items, also used for payment example payment for transportation and some people had no bitcoins, in additional we need a deep learnings how to improve bitcoins to achieve it. goodluck to us., 
Yaa you are exactly right that bitcoins can not replace the money. Bitcoins may be able to use for small payments as well but most of the countries wont be able to allow bitcoins and regulate it. And also all the countries in the world be will able to use bitcoins as it is not well developed.