An inflationary currency is simply one that has an increasing money stock. So, yes bitcoin is inflationary because additional bitcoins are being mined, but it has nothing to do with the price of BTC measured in fiat.
Well it does to some extent. If x new BTC are being added to the exchange each day (net BTC inflows) then y USD also needs to be added (net USD inflows) or the exchange rate will drop.
The higher the exchange rate goes the higher the y/x ratio must also go.
But when your daytrader, you may buy and sell the same bitcoins/USD many times during one day.
So the y/x ratio does not matter much in my opinion