RPC Standards #35: unmerged Geth PRs block V1 spec release, clients still lack unified trace-output spec
This RPC Standards working group call found that a handful of unmerged Geth pull requests are the main blockers to finalizing the eth_simulateV1 specification, and that Ethereum clients still disagree on how to format transaction trace data, delaying a shared trace API.
More: Ethereum Magicians