A single blockchain can’t fit all use-cases, but all blockchains can be useful.
Implementing all possible applications and use-cases on one single, all-encompassing blockchain doesn’t make sense. Data sharing, decentralized content production, transactions, smart contracts, tokenization, etc would reach the technological limit of one ledger in terms of capacity and memory too fast.
At the same time, applications benefit from access and use of each other’s data. To do this securely, these applications have to be on a mutually intelligible blockchain to be able to reliably access each other’s state. If applications end up on separate chains, there needs to be a protocol for the secure exchange of data between these two networks.
Are we going to have hundreds of blockchains? Yes.
Each blockchain will be designed and purpose-built for its specific purpose. There will have to be interchain protocols and interoperability between the chains — developed by and agreed upon by all participants. Interoperability makes it possible to create, deploy, and operate cross-chain or supra-chain decentralized applications.