I think as technology grows there will be a shift in the way we use and perceive money/currency in general. "They" (all of mankind) used to exchange goods with things like salt and precious metals. Now for the most part they use fiat, which requires physical transmission, storage, printing, and centralized entities such as the federal reserve to remain in circulation. Eventually, it makes sense that cryptocurrency is the most logical step in this natural progression. It's still very early, BTC is not even 9% as old as the Federal Reserve, and the dollar is still very strong. In addition to this, POS systems and payroll/tax situations are years behind. Bitcoin will most likely end up being a primary currency, but until then it should remain a strong alternative investment, due to the simple fact that there are trillions of dollars worth of wealth in the fiat system that will eventually move elsewhere.