More then a decade passed since the mysterious Satoshi Nakamoto published his ingenious white paper thst presented the concept of blockchain to the wide world, yet the technology is not adopted at the industrial scale. The main challenge is interoperablity, or rather the lack of it.
Though there are at least 6,500 major public and corporate blockchain out there, they barely talk to each other. Hence, at present dApp developers cannot convert from Ethereum to EOS and vice versa. Protocols for such exchanges are yet to be established.
The future of the distributed ledger technologies depends on the ability of various blockchains to interact with one another.
Also, concepts of decentralization and blockchain interoperability are inter related. So far decentralization has been fully achieved within a blockchaim network.
Currently, the following projects try to solve the challenge of interoperability: Loom Network (targets dApp developers), OriginTrail (works with business standards), Polkadot (aims to become a foundation for decentralised internet), Cosmos Network, Determint, ABGI (these projects work on settlement layers and protocols, IGON, Aion, Wanchain. The three latter has formed Blockchain Interoperability Alliance.
ICON attempts to connect independent blockchains without additional intermediaries. Aion intends to become the common protocol. Wanchain is a platform that enables cross-blockchain smart contract execution.