It's in v5.4 which is currently in development. No ETA but I expect it before the summer. Adapter entities are now 40% of what they are in v5.3 and all code left is simple boring properties and 1-line utility methods (like the prefetch path properties or the methods which produce a relationpredicatebucket for a navigator). This is a slow process but necessary. We also want to reduce the number of files which requires migration task performers as well so it'll take a while to get this right.
We hope to add more features in v5.4 but it's likely we'll release an EAP first with just this update so people can test it.