Thank you for your reply. Still not clear what we getting.
 
On my desktop, I have Dimension 1.5, Rapture full version (paid update) and Z3ta2. I have some 3rd party Rapture libraries as well.
 
So lets say I install on my desktop computer. What did you sy will happen with Dimension and Rapture I already have? Will they stay unchanged, yet many duplicate samples will be installed because Rapture Pro has the same samples as Dimension and old full Rapture?
 
Now different scenario: lets say I installed new SSD and Sonar Platinum. Lets say- I buy upgrade Rapture Pro. Do I need to install Dimension and old Rapture or only 3rd party libraries for old Rapture? I thought that Dimension and Rapture now united in one software and Rapture Pro will install Dimension and Rapture samples and there is no need to install old synths. Please, correct me. Thank you.

Dimension, Rapture and Rapture Pro are completely independent synths, and do not rely on each other being installed.   What Rapture Pro can do is read Dimension and Rapture libraries, as long as they are in the location that Rapture Pro expects.   
 
I don't have Rapture Pro yet but from what I've read it (by default) reads its libraries from a different location than DP and Rapture, so that's where the "duplicate samples" come into play - you could have them from your original DP and Rapture installs and then again with Rapture Pro in its new location.   But if you only install Rapture Pro on a new machine, then you'll only have/need a single location for everything, and that's where you would install your DP and Rapture libraries (without the synths themselves).
 

You saying, DP. Does it mean Dimension Pro? I did not install Dimension when upgraded to Sonar Platinum, so I must have Dimension 1.5 then? So if I install DP, it going to duplicate all the sounds again? And then I install Rapture Pro and it will duplicate Rapture sounds? Is there clear explanation from Cakewalk regarding what is what? It looks like they offering the same product in different packages and don't want to mention that it duplicates what we already have.
Also if I install on new computer Rapture Pro, it will not install Dimension Pro? DP is not part of RP? Thank you.

Will Dimension Pro and Rapture Classic factory content be available in Rapture Pro?
Yes. Just like expansion packs, all factory content from Dimension Pro and Rapture Classic that was installed before Rapture Pro will be automatically migrated.
Note that the Legacy Content Packs Vol 1–3 included with Rapture Pro contain the Dimension Pro and Rapture Classic factory content. If Rapture Pro is being installed fresh, Dimension Pro and Rapture Classic factory content is available in these packs.