I’d say given the recent developments in the Alphatheta/Serato takeover, the likelihood of InMusic working on anything Rekordbox integration related is extremely slim.
That tool in Engine was only ever designed to be a starting point for people moving over from other software. Once in Engine you’re then meant to use that as your library management tool.
At this point you’re better off looking to adapt your workflow and not sit around waiting for something that’s unlikely to be implemented.