I don't consider myself an expert here, but I believe there are few or no problems that only blockchain technology can solve. Rather, it's about how it solves problems. If you solve a problem with non-blockchain technology, you will get a centralized entity of some kind. Be it a bank, a SaaS service, a social network, a database, or whatever. Sure, it can be open source, but it's still centralized in one way or anoth…
A well designed decentralized system will maintain its integrity indefinitely. In practice we've only really seen this play out with Bitcoin so far, but that's because the space is young and people still haven't really gotten their heads around the exact strengths and weaknesses of a blockchain.