A few years ago there was a large hue and cry about Cakewalk's slow move to VST3. Most of the uproar came from big library user who wanted the benefits that the VST3 spec brought to the table.
Finally in Sonar X3 VST3 was implemented but not fully. There was a continuing complaint about what part of the VST3 spec was not implemented in X3. From all accounts Sonar Platinum has added some more of those missing pieces with of course development in how fully the VST3 spec is implemented.
I know you don't want moving to Platinum to be on the table. I just want you to know that you will be missing out on developing features as they apply to VST3 use no matter what library you use.