Why need to be replaced? Why not just look for a platform can offer like what etehreum does.
Remember that in time when the crypto is represented and accepted world wide all of this currencies will have their own time  and service and believe me they won't sustain the needs of the world so
there is no need for this question ,instead make sure that those currencies ar elegit and make the services we needed for anything we need.
and also Ethereum is a Strong platform that stablished His own position  ,so Bringing this back will take long and capacity for sure.