In the end in the case of X3. Like me you will always have that version available to install as long as there is a OS that will run it. There is no danger in messing it up by installing CbB
So personally I'm not going to worry about what might happen to my older versions because I will probably never open them again anyways. 
There are many improvements to the new versions and if you use MIDI and the PRV your're really short changing yourself by not upgrading. 

YES!!YES!!YES!! I forgot to mention the AWESOME NEW MIDI & PRV IMPROVEMENTS!!!!!!!

I have read and reread Scook's reply--as well as the others that followed it--but still don't see an answer to the main question I had posed. I DO realize that any plug ins or other virtual effects/synths I already had would NOT be removed by  installing this new software (as long as I don't uninstal X3.) However, as some of the other participants have said, it might take a while to learn this new software, and it's true that time is very scarce for me (I'm not dying, I just have an unrelated job that takes a lot of time.) However, if this new version had most of the content that I saw has been added to Platinum over the past few years, it would prob be worthwhile. As I had said, that Vocal SYnc, which, I believe, would help me align vocal tracks when I sing two versions of the same song to get my scrawny little voice to sound more full---that would be probably be worth the time in updating alone. However, as I had said, I thought I saw somewhere that some of these 3rd party software updates were NOT going to be included with this free version. I realize that there are multiple other technical aspects of this new version which do appear to be much better, but it would be nice to know beforehand what will and will not be included.
Thanks again for your time.
LNovik

Yes, coming from X3 there will be a little bit of a learning curve because you're going to get new features that weren't in X3. A small price to pay for a free upgrade!
 
Meanwhile, X3 will continue to work just fine, so you can finish up any works in progress with the version you're most comfortable with and ease into CbB. That's how I coped with the change when I went from 8.5 to SPlat, a much bigger jump than X3 -> SPlat. 

From the replies, my guess is that perhaps some people are not sure which 3rd party programs are included, and which are not--which is why my question does not seem to be answered.
I went back to the original announcement by BandLab a few weeks ago, and they said: The big news is a business model change that is only possible because of our ecosystem – we’re releasing the entire feature set of SONAR Platinum (sans certain 3rd party plugins and content) in its new form of Cakewalk by BandLab completely free.
So, I still have this main question: when I look at all the 3rd party updates in Platinum in the past 3 years, such as 1)Vocal Sync and 2)mastering tools, Wwitten as "six brand new Mastering Templates that master your mix in seconds." and 3)Les Paul Gold Top Expansion Pack---are these some of the 3rd party plugins that will or will not be included? ALso, is this software free to everyone, or just those updating from other Cakewalk versions.
Thanks.
LNovik

What BandLab has released so far is similar to the SONAR Platinum and Artist Instrument Collection installers. The two BandLab installers are Cakewalk.exe and Instrument.exe
1) VocalSync is built into the DAW and is part of CbB now.
2) CbB includes the 6 project templates that were in SONAR installer. These are not the 6 Mastering templates added later. The mastering templates were in a different installer. Since you are coming from X3, when BandLab does port the new LP EQ, LP MB and Adaptive Limiter, you may not get those for free. The plug-ins are not available from them at this time. so I can't say for sure.
3) That was a separate installer so it has not been released yet.
The rest of the SONAR plug-ins  and content need to be ported before they will be available from BandLab.

Not sure if this was mentioned for the OP, but aux tracks made cwp files not backwards compatible. I have not seen if this was ever changed, but may have been. What this could mean is if you use them and revert to X3 that those cwp files will not open.

Thanks. That's clearer.
LNovik

I have only x3e and then I scored the free copy of the new Home Studio. 
I jumped on the CbB right away. 
For me there has been no noticable differance between HS and Bandlab version other than some better features. Most I'll never use, but cool,, they are free. 
It's been nice to have been given both these new versions free,, I recommend just installing it and that will answer your question right away. And I have opened X3e a few times since and nothing seems broken. 
And CWP files from Home Studio seems to open in X3e. Haven't tried any Bandlab stuff yet but will just to test when I get a minute. 
 
The coolest thing so far is the this fancy Pro Channel comes with a lot more than it did in HS. That has made it worth it alone. Didn't like the new PVR darkness but scook posted how to fix that somewhere here. 

sock monkey
Didn't like the new PVR darkness but scook posted how to fix that somewhere here. 

The fix I provided only works for Platinum users. For those coming from other versions, it might be easier to switch to the Mercury theme. It looks and works like the X3 UI. When the new theme editor is released there may be more options.