Bitcoin can also be devaluated by lost of trust. Also the current supply of Bitcoin is through mining only.
If rules are changed by a fork then you will have 2 different coins. We already saw it with bitcoin cash. Another way would be that the current consensus on Bitcoin itself changes. But that's a risk. How can people then predict such a consensus change. How risky is it to have Bitcoin since the day after the rules may change ?
Bitcoin could be forked in the future to become inflationary. It has no permanent rules, things can change through consensus.
It isn't like gold (gold can be devalued through poeple losing faith in it, etc., but the supply of it doesn't inflate other than through discovery/mining).