Because bitcoin can do these things, can it be considered a currency? No, because it can't do them alone.

The price of the things youre buying with BTC are, for the most part, denominated in dollars or euros or whatever-- in an actual currency. So, for example. Lets say Cryptic Pizza charges a dollar for a slice of pizza, but they allow you to pay in bitcoin. There is no "bitcoin price" there is a set dollar price for bitcoins and a set dollar price for pizza. The exchange of two things are mediated by the dollar, even though dollars are never actually exchanged. The ability to do this -- to set valuations for two independent things in order to mediate their exchange, is what makes a dollar currency.
In the very same way, i might arrange to pay for my pizza with $1 worth of pepperoni. That does not make pepperoni a currency. The reason for this is that the owner of cryptic pizza has to pay for rent, gas, electric, dough, cheese etc with dollars, not with bitcoins..

The owner of cryptric pizza has to charge enough to cover his expenses and make a profit. And, for the most part, he can only pay those expenses in dollars.

This is because it is not possible to exchange bitcoin for a wide enough basket of goods for it to actually have an independent valuation against something like a pizza.

Now, you might be asking, is it possible for bitcoin to become a currency, once its gained wide enough adoption. Sure. currency evolves from commodity. But in order for that to happen, it has to gain much broader marketplace acceptance.

Incidentally, one might argue that in the very narrow marketplace of altcoin trading, bitcoin is, in fact a currency.