Our current stored Parsoid HTML is not consistently up to date with the advertised stable HTML spec version. This is starting to cause issues for clients (ex: T155070), so we should address this soon.
We have a generic content versioning filter ready that can enforce the latest HTML spec version by re-rendering the content, but we would like to take advantage of this change to also change the database schema. T156199 tracks our current plans on the database schema change.
After the latest deploy of Parsoid where they've changed the styles, we're seeing very low rates of re-renders with the same HTML, because every page was affected by the change. So the issue is getting much less pressing now.
Yeah, I agree that at this point we should be able to just do it. In any case, the upcoming v1.5 bump will invalidate everything again.
As of yesterday (June 26th), HTML spec virsion 1.5.0 is deployed, and all stored content in RESTBase is being upgraded by the generic content type upgrade filter.
So, calling this one done.