Thanks, all!
I was aware of the Bit-Bridge scenario. My past experiences, however, were much like tenfoot's. Instability. Also, there are still some 32 bit DX plugs I still really like, also (Thanks, scook, for that reminder).
Actually, my only reason for even thinking about eventually switching over to 64 bit is just to keep up with modern times. Ha ha! I guess I don't really understand the benefits of 64 bit over 32 bit. (I know you can address way more memory but, I've never found the need for more memory, personally.) I guess, a fear that, eventually, 32 bit will no longer be supported and we will be forced to go 64 bit is my only real reason for even thinking about it. Am I missing something?  

I believe the problem with 32bit DAWs is plug-in support. By now, I suspect most plug-ins which do not have a 64bit version probably have not been updated in some time. Some older plug-ins require registry hacks or administrator privileges to run. Some require legacy windows libraries. Even if 32bit DAWs were always supported; it is a matter of time before the OS is updated to the point old plug-ins will no longer work.

I agree tenfoot that bit-bridge was kinda buggy in Sonar X series. But I have found Platinum to be extremely stable. I use multiple instances of 32bit Nexus and Massive which we all know can bring a big session to a halt and I have not had any problems. I am using Windows 8.1 so that may be the reason for the stability.

Scook, Direct X totally slipped my mind as most plug-ins that come in that technology can also be installed as VST2. Unless it is extremely old. But you are right.

scook, I am trying to replace all my old, favorite 32 bit plugs with shiny, new 64 bit plugs. I'm getting close but, still got a couple things to replace/learn to live without.
One thing.... when I open some projects previously recorded/mixed in 32 bit X3 in 64 bit Platinum, I swear, they sound slightly louder/harsher in the upper mids/highs. Is this even possible or, is my mind playing tricks on me????

The conventional wisdom is 64bit sounds no better than 32bit. I have not read anywhere the claim that it sounds worse.

Very subtle but, I swear, I hear a difference. Strange. Not specifically worse, different in the upper mids and highs. If I play around with EQ and levels, I can bring it right in line with the 32 bit version. Maybe some 64 bit plugin is a bit more efficient or reacting just slightly different than it's 32 bit counterpart??

I changed to 64bit for exactly the same reason Rob - I just saw the writing on the wall for 32bit Plugins and eventually Windows X86 itself. It was relatively painless though, as I found that most plugins now have a 64 bit version, and as S Cook said, if they don't they are quite old. The big advantage was that it forced me to make changes that, being a creature of habit, I had put off. Many of these out to be a massive improvement,, like moving from Sample Tank 2 to 3, which sounds  amazing. 
 
In the process I also came to realise that it was time to let go of certain sounds and effects that had been long time favourites. For example, my go-to reverb for individual backing tracks for my live show was Lexicon Pantheon, from Sonar 8.5. I erroneously thought that it was a 32 bit plugin, so began the search for an effect that sounded exactly like it. After a couple of hours experimenting with Breverb 2, although it didn't sound the same as the lexicon, I much preferred the result. I guess you could say that the process taught an old dog some new tricks:)
 
Once everything is 64bit you will be amazed at the performance difference that the extra ram makes. One tweak that I found particularly effective once I changed over was to disable core parking. There are many threads about it on this forum. 
 
Interesting that you are finding a difference in sound Rob. I know that the much faster loading and response time of Sonar in x64 makes me think that the whole world is better:)
 
Glad to hear that you are finding bit-bridge more stable in Platinum Tino Red. I think it is all round the most stable upgrade we have seen in a long time - well done bakers!
 

tenfoot: I agree 100% with what you're saying. I know the change is inevitable. I just don't have all my 64 bit go-to plugins in order yet.
The Lexicon Pantheon is still my favorite reverb as well. I'm really trying to love Breverb but, so far, I'm just not as fond of it. Maybe I need to spring for the (paid) full version??? Maybe I need to buy some other reverb?? Maybe I'll learn to love Breverb??
 

I hear you Rob! The good news is that the Lexicon is 64bit, so you can still use it. I do use the full version of Breverb. It took a bit more time to get my head around than the Pantheon, which I found I could dial up a preset and with very little tweaking be on my way. With Breverb you have an awesome amount of control and many extra variables, that I, at least, was not familiar with. Spend a bit of time tweaking those extra parameters because that is where the magic is:) 

Make sure to check out the REmatrix Solo ProChannel module.