I just got an Java update notification that Update 17 is out, so I ran the update and found that only my public JRE was updated. I still only have Update 16 of the JDK.
Not on Windows. If you are getting your JDK via a linux distro with an auto-updater, you could depend on that. Somehow I doubt that is what you have in mind. I do not believe that there is any Sun-supplied auto-download for the JDK.