I just wanted to note that 8.5 on OSX seems to default to 32-bit mode. Be sure to change to 64-bit if you desire to work at 64-bit.
Also, Wavelab 8 seems to remain installed, so you’ll have to be sure you are launching 8.5 from your applications folder, you can’t continue to use the same icon in your dock as you can with other apps that update.
So 8.5 actually gets installed as an additional application, i.e. if I have 8.0.3 installed, and I install 8.5, 8.0.3 doesn’t get updated, instead a whole new installation of 8.5 is added?
I installed 8.5 using the installer, and can still launch 8.0.3 if needed. So yes, both versions seem to be co-installed on OSX.
Just be sure that you use the 8.5 app icon in your dock as 8.0.3 and 8.5 appear the same to me.