There are emerging cryptocoins which don't rely on the 'old' blockchain technology. The most known of them are IOTA and NANO (raiblocks).
I have never used these coins so far, but their developers state these coins can provide a lot of improvements and better features than traditional blockchain-based cryptocoins like Bitcoin. For example, faster and cheaper transactions, less energy consumption and so on. So do you think blockchain-based cryptocoins are doomed and the future will be favorable to these emerging technologies?