The supply is inflating until we reach 21 million around 2140. So it is an inflating currency until that time. Because it's new and adoption rate is rising fast the price of a bitcoin is going up, but this doesn't change the fact that the total supply of bitcoin is increasing at about 10% per year right now. This is the very definition of inflation.
Inflation: The rate at which the general level of prices for goods and services is rising, and, subsequently, purchasing power is falling.
The purchasing power of
BTC rises, so by definition its not an inflationary currency. The fact that a 10% of btc are emitted yearly at the moment is overwhelmed because of the increase of users getting btc. Also the amount of emitted gets reduced every few years, most of the coins will already be mined by 2020.
In simpler terms. Imagine a country. Population 10 habitants. The total emitted currency 10$. Every year 1$ is added to the total. So next year you have 11$ for the 10 habitants. But that year 90 more people immigrate to your country. They are all forced to adopt your $. They have goods to exchange for it. But given that 100 people have to live with a total of 11$, and new goods where introduced to that market, the purchasing power of those 11$ is much bigger than what it used to be. Making that currency deflate, even though more money is emitted every year.
Now imagine what would happen if a few million people get into
BTC 
