I think that global adoptation and mainstream use of the bitcoin as a day to day currency is hard to achieve, and that is due to the fact of  it being decentrelized and uncontroled meaing that the price will always be constantly changing at any time, so a guy who owns a shop could sell a product that is worth 10$ and the next week finds himself with only 5$, for somone who is earning more than enough and wants to invest in bitcoin he could start accepting as a apyment method in his business but from somone who his trying to make a living it would hard, at least this early.