Maybe IOTA could be good replacement. They still have prove their tangle technology can stand the test of time. But transactions are totally free and fast. And there's no scalability problems. The more it's used the faster it gets. That might make it the ultimate coin to buy alts.
Bitcoin as well some alts may not die, not this time or not too soon. Because I can visualize that btc will be the future money because it is the solution on money finance system problem