Yes, people may be able to live their life without going back to USD currency, so their will be no devaluation of a crypo X as long as people trust it (as gold). When a cryto X is not trusted anymore people are going to stop using it to go back to USD or another crypto thus devaluating the cryto X in respect to the USD.

A big advantage of cryptocurrencies (I think) is that there is no regulation (no central bank injecting billions), but it is also its Achilles's heel because it can't be used ha s a commodity currency because it miss the stability of a currency backed by a central bank.