For the record, the vote [lazily] passed, and the PR <https://github.com/apache/airflow/pull/21816> was merged.
As Ash has noted, this will in effect make conn.extra and conn.extra_dejson redundant (since, by requiring extra to be json, there's no reason we can't store it as a dict in the first place). But we have to think it through, particularly regarding backcompat strategy, and for now this is left unresolved. And I agree with Jarek that we should improve certain aspects of the custom fields. I can think of two issues: empty string as default value and ugly keys (e.g `extra__google__keyfile_dict`) -- would be good to hear what other areas of improvement you have in mind Jarek.
