Just thought I'd share what I'm seeing with this.
I have a pile of plugins still under WUP and a pile of plugins not under WUP. On the Waves site I updated all the WUPed plugins licenses. The site had a list of everything that was still under WUP, I checked them all and did the license update. I installed the new Waves Central. Then I transferred all the new licenses to my USB thumb drive. Then I installed all the V10 plugins Waves Central listed for me but I declined all the offers to uninstall V9 (since it uninstalls all V9 plugins). I did pick the option to install and update when doing the install though (strange dialog early on the install process)
Since I only use the VST3 versions of Wave plugins, inside Cubase 9.5 and SONAR/Bandlab (tried both) everything is pretty much what you'd expect, when I load a plugin that I have a V10 license for I get the V10 version. When I load a plugin I have a V9 license for, I get the V9 version. But in Reaper I see two copies of every V10 plugin. One loads as V9 the other as V10. In SONAR and Cubase these V9 versions are hidden. Though SONAR/Bandlab shows the old 9.92 version number in the Browser window status bar, when it loads it is the V10 version. But in Reaper I can actually load the V9 version of plugins I have V10 versions of.
If you look at the two Waves plugin dirs:
C:\Program Files (x86)\Waves\Plug-Ins V9
C:\Program Files (x86)\Waves\Plug-Ins V10
I see bundles for every plugin in both directories. So the V9 plugins are still there, and V10 versions of plugins I don't have V10 licenses for.
A while back I upgraded my Gold and a few loose Ren plugins to Gold+Ren, which let me trade in those loose licenses and get a new Gold+Ren with a new WUP at a big discount. Buying an upgrade as a way to get new plugins plus WUP (and in this case V10) may be a better deal than just paying for WUP itself. Depending on if you have loose licenses to plugins that make up the bundle. I'm sure there will be more upgrade/WUP games that can get the price of going to V10 cheaper.
I'm really at a loss why they released V10 with not a single updated plugin. That seems crazy. I'm only going to WUP if I get something out of it, and right now V10 offers nothing. Strange.