It seems you have your definitions mixed up a bit.

Purely deflationary currency means its supply is frozen. Technically Bitcoin is inflationary, because new supply is constantly added to the market. If demand exceeds this supply, there can be periods of deflation, when prices drop, but this is deflation of goods priced in that currency. However monetary inflation of Bitcoin is still there, although it may not be visible. Here is a link for you: http://en.wikipedia.org/wiki/Monetary_inflation

Only Proof-of-Stake currencies can be considered deflationary in the strict meaning of this word, because their supply is fixed and not growing after genesis block.

Bitcoin will become deflationary when the last bitcoin has been mined into existance, but it's still a few years away.