Yes sure they are still king cause it hasn't been eliminated from the phase of being used as a legal tender but then people tend to abandon it cause of it's devalued state,you can decide to hold on to crypto and digital currency for so long but once it's been exchange to a fiat currency like paper money within minutes you can't give accounts of how it was spent,so this is a more reason to prefer other medium than cash in hand.
Cash will gradually be eliminated due to the advancement of technology and the world is moving towards digitization of everything, and this has nothing to do with inflation or currency devaluation. Once cash is eliminated, CBDC will be the alternative or another currency issued by the government and they will also lose value over time. Because they are basically the same, both are issued by the government and can print more whenever they want.
I also believe that cash will be eliminated completely but I don't think bitcoin or cryptocurrencies will be used to replace it. The government will never accept bitcoin or cryptocurrency...or any currency not issued by them. Instead, digital payment methods or CBDCs will be the alternative.