We are already moving Neki customers into production. Nobody else is even close. PlanetScale doesn't spend our days yapping about what we are going to do. We just do it.
I am sure there are ways the Drizzle and PlanetScale will be able to integrate. If we do it will all being using open specs and standards so other database providers can leverage the same features.
In terms of expanding to other languages, this has not been discussed but never say never I guess.
It's a durability thing, we need to make sure writes are replicated off to at least one node. There might be avenues to get Metal down to single node in the future.