Its neither, bitcoin is supposed to change the global paradigm of stored value.

A commodity is a resource that can be sold and bought for expected gains/loss in the future.

A currency is a transactional tool for goods and services and is a store of wealth, albeit fixed.

Since Bitcoin is still in its growing pre-pubescent stages, its temperamental and subject to wild price swings. However if you look at every exchange, it always has BTC as a medium to buy alt currencies, in a sense it is already being used as a currency.

As for a commodity, we view it as one, and temporarily it is being treated like one, but in reality it is not. Oneday will be $1million a piece, its price will vary about 1-2% p.a. and people will use it as the fundamental store of wealth in a new digital economy.