I roughly know that is needed, this time round

- take the taproot data model and apply expand ways it can be used
- structured profiles that can have developer defined extensions, e.g. for subkeys
- tighter integration with on-chain transactions allowing timestamping, versioning and smart contracts
- uniform caching and scaling interface, layered, stateless, with CDNs and proper etags
- proper json based data models with schemas that work, can be versioned, have an audit trail
- schnorr signatures over simple json data structures, as today
- lightning fast profile and roster apps, allowing things like chat
- personal storage, access controlled
- everything payments ready, with audit, and observable reputation
- close AI integration so that nostr builds itself
- proper web of trust including punishment zaps for bad actors, spammers, scammers
- wide range of micro apps, including chat
- incentive structure to support long term growth, on a level playing field

and so on ...