I think eventually it may be taken at retail stores and shopping malls, but I think a lot of places will shy away from trading in bitcoin because the price fluctuation is so volatile. What I see happening is that there will be machines similar to ATMs where you can exchange bitcoin into whatever local fiat currency used, and then trade from there. I think we're a couple years off of that happening mainstream, but that's how it'll go. Another possibility is that another altcoin that is specifically used for retail purchases will be developed and you can exchange your BTC into that to make purchases. Either way, it'll be a few years at least.