Anything's possible. For now BTC and ETH have network effect. Their value is multiplied by the strength of their respective networks. Newcomers have to advance to such a degree that users would find enough value in features and abilities to overcome the network effect and leave the incumbent platforms. Not impossible but unlikely.

Also consider that we don't really know how much room there is for competition when the technology breaks mainstream across the globe. Will there be hundreds of massive chains or a small handful? That too will factor into the longevity of existing networks.