If 32bit plugs work...

and sound OK in my 64 bit SonarX3PE, why would I *prefer* a 64 bit version?  Perfect Space comes to mind.  Works great, but would/should I expect to hear an improvement or better computer resources, etc...if a 64 bit version came out??  It's not like my StudioCat computer is struggling or anything.  I go pretty light on the demands it handles anyways.

Because it is an indication the plug-in is being developed and maintained.

If your effects are working for you, there is no great reason to change. If they are incompatible or unstable, you will know it soon enough. Versions that are native 64-bit could possibly be written to work more efficiently (if you have sufficient memory installed), but may not be so in every case. If you are investing in a new plug, then you are more likely to be able to keep it in new versions of Sonar etc. if it is native 64. The history of computing is that newer versions eventually replace older versions, if not because they offer better features, then because they are rendered incompatible by developers who cannot afford to support old stuff that is not making them any new sales.

Anderton
Short-term, bridging 32-bit plug-ins in a 64-bit host running in a 64-bit operating system opens up opportunities for instabilities that would be less likely of an issue in an all 64-bit system.
 
Long-term, scook states a fundamental truth 

Would I be wrong to assume Cake feels Perfect Space, therefore would not cause problems, or else they might have opted for a 64bit convolution reverb for a replacement...or maybe one is coming in the future or Perfect Space might be updated??  ...or none of the above?

I got Perfect Space with my X3 purchase and although I don't use it a lot...works great.  Breverb in the ProChannel and as an FX bin selection has been too easy to grab and almost dominates what I use nowadays, however.  For some reason, I'm not finding the pre-delay in the ProChannel module version (unlike the FX bin selection) in all the reverb types... like "hall" for instance.  It's on the plate and I think the "room"....but..not hall. Might be my error as I've looked a couple times, didn't find it and just moved on...  But...that's a rabbit trail to my original topic.

 
If it works for you now, it's very unlikely to suddenly stop working anytime soon. It's a great convolution reverb, more versatile than many others. Go ahead and use it. I can think of no reason not to.
 
Yes, it's true that PS will not be developed further. Aleksey has even dropped his own version because it wasn't selling well. So yeh, it's a dead product. But so what? It's stable and sounds good and doesn't lack any important features.