I've heard a saying "just say no to dot oh" -- encouraging one to skip the .0 release and wait until .1 or .2 before doing the upgrade.
I think that's a nice compromise; although not a "real" test as the load is a lot less. Also things may work in dev but not production, but unless you explicitly use new features that's rare.
For larger setups you can us canary servers and whatnot, but I prefer to work at small companies and keep my sanity.
I do like the idea of "canary versioning" some stuff. It's a bit of a game theory issue isn't it, since we all need prod to work at all times and can't risk a .0, and a major version difference between dev and prod can mask some nasty issues in my experience.
Unluckily, chances they will report bugs not that high - at least I don't expect bugs related to any moderate size/loaded databases be found by this way.