"Maybe if they decide to evolve from SQLite to something like Postgres"
Yes, if they went that route with a properly functional dbms it could open up some interesting possibilities, with a distributed catalogue and multi user support. On the other hand, there probably aren't many DBA's among the Lightroom user community!
As an aside, mention of Postgres reminds me of the database wars back in the 80's with Mike Stonebraker's lot slugging it out with Oracle. For a while we also used Britton Lee "data base machines", another offspring of the Berkley group.