Truthfully, Bitcoin can potentially increase as well as to preserve purchasing power, but does that automatically imply that it offers a guaranteed inflation hedge? Definitely not.
While fiats can steadily lose purchasing power, let’s not forget that even Bitcoin can also experience a very large decline too, so for someone who needs the money in the short term would still find themselves in a bad position. So I believe the most important factor that makes Bitcoin more attractive and a better option is the time horizon as well as the ability to hold through volatility.
The correlation between Bitcoin purchasing power and fiat currency power is quite opposite, with fiat currencies lost their purchasing power with time as consequence of inflation or hyper inflation depending on rates of money printing in different countries. With Bitcoin, it's programmed to have Bitcoin block subsidy halves every 210,000 blocks or 4 years. This supply vs time scheme, together with lost bitcoin in the past and the future, make Bitcoin supply is deflationary.
Deflationary is only one of many things that make Bitcoin value but together they all make Bitcoin value rising with time. As a result of that, we have a very good wealth storage, store of value asset, Bitcoin against fiat currencies.
Simply see
https://charts.bitbo.io/satoshi-per-dollar/
