Data source v2 API is one of the larger main changes in Spark 2.3, and whatever that has already been committed is only the first version and we'd need more work post-2.3 to improve and stablize it.
I think at this point we should stop making changes to it in branch-2.3, and instead focus on using the existing API and getting feedback for 2.4. Would people be interested in doing an online hangout to discuss this, perhaps in the month of Feb? It'd be more productive if people attending the hangout have tried the API by implementing some new sources or porting an existing source over.
