We have worked on a first draft for the specification of the FA2 update: FA2.1 - HackMD
The goal of the FA2.1 extension is to include new protocol features while remaining fully compatible with current applications that rely on the FA2 standard.
Events are a means to solve discoverability problems encountered by indexers, i.e. to know when a token is transferred especially outside the specified transfer entrypoint (mint, burn, etc…).
On-chain views are a means for smart contracts to share information easily. Callback views are kept for compatibility with already deployed contracts.
Tickets are a way to materialize tokens outside of smart contracts. They can be transferred without calling the creator contract and affecting its status. Tezos rollups rely on tickets for representing Layer 1 assets on Layer 2.
Additionally, finite allowance, enabling a user to grant permission to spend a fixed amount of tokens, is introduced (based on the FA1.2 scheme).
