When is Cinnamon 6 expected to drop and is it an automatic download?

It's updated whenever your package manager puts up the new version. If you're using something like Ubuntu or Mint, then you're using apt as your package manager, which takes a while to update stuff because they like to test it for a while first.

Its supposed to release early next year but if you're on the stable channel it might be a little bit more of a wait. Someone can correct me if I'm wrong but when its released and you run your system update, cinnamon will be updated.