No one is arguing deflationary nature of bitcoin here, since it is exactly the cause of those pre-fiat era crises (i.e. deflationary nature of a gold backed dollar)
Well, the amount of BTC in the world will continue to expand probably for at least another century. So I'd say it's incorrect to simply say that bitcoin is deflationary.
The origins of terms inflationary and deflationary are quite different. Deflationary in respect to currency means that it is appreciating in value (i.e. gathering purchasing power), since the word deflation (unlike inflation for which at least two different meanings coexist) means first and before all decline in prices...