Although of course it seems unlikely, all good things must come to an end and someday, in the distant future, the blockchain technology will fail. When it happens, what could replace it? Is there anything out there that functions similarly and just as good and reliable as blockchain? More importantly, if nothing replaces it, what will happen to cryptocurrencies then? Any ideas?
First of all, I really can't think of any foreseeable reason why the blockchain that is underlying the bitcoin network would fail.
As long as there are people using it, and that the network doesn't get exploited big time (which it has shown the ability to be secure over the last decade), then blockchain will not "fail" and will continue to run even if prices do drop drastically which I don't think is that probable either.
Potentially quantum computing will see problems for blockchain, but right now, that still seems distant. But for sure, it's not like blockchain is going to be something that will not be replaced in the future by potentially better technologies, but it's the best practical one for decentralised online transactions right now. I'm not sure practically speaking anything else would be able to replace it at the moment.