I agree with your thoughts about the bus, but I started thinking about how many car brands started out selling practical cars, and now have, if not supercars, very high end sports cars - it's a lot of them. It's also kind of how Apple has done stuff in the past. They've marketed their "lesser" products by also making sexy, "pro" products. They could have easily done the same here. Release a practical, functional, Apple product, stuffed with Apple's attention to detail, followed up with the supercar. The keynote would look just like any Macbook lineup update, with the $20k model saved for the end.
But a bus? Yeah, that's just weird.