Reinstalling from online (you must use the online option) does install the most recent version, short of that I've never found any other way to update Waves plugins. And there is no way to uninstall single plugins. You have to uninstall everything (using Wave Central) and then reinstall.
If you look at their change log page, they do make updates all the time. I'd also point out that this isn't a WUP thing. Many of my plugins no longer have active WUP but you can still continue to install newer versions up to the current major version. So until they release version 10, your current licenses will work with all the version 9 series (assuming your plugins are Version 9, if not you'd have to WUP them to go from Version 7/8, etc).
If you are doing this update you may want to consider if you want to include the Multirack/Studio Rack/SoundGrid Studio stuff (they gave this away at one point so I'm guessing lots of people have it), it usually requires a reboot since it installs some audio device drives. It's the only one I remove before installing unless I know for sure it's had an update.
The Waves change log page is here:
http://www.waves.com/downloads/release-notes