Well, when Cubase Pro 8 was first released, Yamaha stated that the Motif XF editor was not working as a VST-Plugin, and that Steinberg needed to make it compatible via a Cubase Pro 8 update.
I got a reply from the Yamahasynth forum that it is compatible at this time.
Yes, makes me nervous too, and sometimes, unhappy.
i.e. I have a Roland Integra 7 Module, which has a VST-Editor that works great in Cubase Pro 8, the VST Editor is only available in VST3 format, so it won’t work with my other DAW (Bitwig Studio). Since it currently does not support VST3.
My other options are using a Standalone Integra 7 Editor, or the iPad Editor, which does not offer deep level editing of parameters.
Funny you should mention the Integra 7. I’ve been looking into for a while now. Good to hear it works well with Cubase Pro 8. Mac drivers and editor seem to be be compatible with Yosemite (OSX 101.10).