Postmodern is very good, it just slipped my mind as I haven't used it except as a reference when implementing my own ORM. But since Postmodern is Postgres-only

Postmodern is very good, it just slipped my mind as I haven't used it except as a reference when implementing my own ORM. But since Postmodern is Postgres-only, and is a very stable, maintained library (and I doubt the author has plans for the future, having mostly moved to JavaScript), it doesn't really fit into either 'future work' or 'consolidation'. As for Elephant, IIRC it's no longer maintained, and I think the model it presents -- just serialize CLOS objects, with whatever backend -- is the wrong way to go about it. Most of the time, it's better to be aware that you're using SQL, or a JSON file, or whatever your storage is.