I don't think it will be a currency, though. Despite its name, it's just not viable without changes to the underlying code. I think an altcoin will take over and be the true currency, with Bitcoin being for larger transfers or just remaining an investment vehicle. A currency relies on ease of use and speed. Bitcoin lacks the latter.
It's still orders of magnitude faster than credit cards or bank transfers. In fact, it faster than any known system.
Also, decreasing confirmation time like many altcoins do only result in needing more confirmations to achieve the same level of safety.
Note that your transaction can be validated instantly, but confirmation may take several minutes or hours depending on how secure you want it to be.
With credit cards your transaction may be validatd instantly but the actual transfer of money will take weeks or even months. Bank transfers will take days or even weeks. And they are way more expensive too.
For your average transaction, what you as a consumer notice will not be much different with Bitcoin from what you are used to. You can use a phone or a card to pay. Your payment will be instant. The benefits are that you have full control over your own money and do not risk a bank or a government stealing or "confiscating" your money, and that eventually things may be cheaper because stores might pass on their savings to you. And you can easily do transactions in foreign countries. A true world currency.
The benefit to the store is that they can market worldwide, have extremely cheap processing of transactions, get their money almost instantly (as opposed to having to wait for weeks), and probably more, but you get the point.
Bitcoin is designed to be a currency, and it is perfectly suited to be used as currency.