We've built a hybrid database that federates workloads & queries atop both a relational & vector component. Right now we've got fairly limited interaction between those two halves of the brain, but it's one of the things that gets me most excited when thinking about potential.
There's a lot of great work going on in this space too, by the way -- everything from PostGres plugins for vectors to vector databases adding relations to things in between.
It's going to be awesome few years to watch. There's a real pull toward finding a way to comfortably merge the two: it enables some pretty incredible queries.