I'm not sure about this one.

The trend is increasingly to use bitcoin as an asset, as well as a store of value, hedge against fiat currencies, and a currency for online payments, both of which is proving to be extremely effective so far. However, if you're talking about real life payments, I doubt it'll go mainstream unless bitcoin itself becomes the world's singular currency or something along the lines of that. Very unlikely in the near future, I'd say.

There is always a chance, but for now, BTC's uses are going to pretty much be limited to online. But as more and more people gain regular access to the internet I honestly do not see a problem with that.