I wouldn't go that far, at least not until everyone is receiving their paycheck in bitcoin and stuff at the grocery store is priced in bitcoin.  As it stands right now, there's a very real need for fiat currency, no matter how hardcore a bitcoin supporter you are.

As far as OP's point is concerned, bitcoin could function just fine as a currency if people chose to use it as that.  Its value would have to increase significantly in order for that to happen, but it's possible.  And I would also say that if people want to keep it as a store of value or own it just for trading, that's fine by me.  Crypto as a whole hasn't caught on as far as becoming a popular payment method--there are tons of coins that function better than bitcoin does as money, yet not many people are using them either.