The roadmap is an active area of research. The outline below is only intended to provide flavour. It is intended for this document to be maintained with ongoing R&D.
Sourced originally from the now retired spec for phase 1 sharding, with modifications.
- State-minimized clients. Stateless clients are not ideal as we don’t want to offload all storage into secondary markets, rather we can give people a choice to pay storage rent on the blockchain or pay for it in secondary markets.
¶ Phase 4: Cross-shard transactions: see here and more.
¶ Phase 5: Tight coupling with main chain security: here and more.
And a lot more: https://ethresear.ch/c/sharding.
For more information see and sharding FAQs.