What I've discovered (so far) is that if you open Dreamweaver cc or 2014 then go to help and check for updates you are given the option to download a new extension manager. This will overwrite the CC extension manager. Then you will see a new menu item on the left for Dreamweaver 2014 (as well as Dreamweaver CC). You can then manage extensions for both versions.
Also, the deprecated server behaviour is now accessible by going to Window and then Add-ons. However I found that as I had CC still installed it just transferred my extensions over from CC to 2014 automatically. My only problem was that I never had the new updated versions of WebAssist's extensions. I am now using the updated version of the Extension manager to un-install and reinstall the WA extensions. So I would recommend that you update your CC installations and then open 2014.
Hope that all makes sense (it's a work in progress).
Yes I have carried all this out successfully. I've also found the if you install/update an extension in Extension Manager CC it installs into both DW CC and DW CC 2014 (That is it installs in the extension manager. You will need to open both DW CC and DW CC 2014 to allow the rest of WebAssist's installation process and activate in each program (CC and 2014).
So to summarise: Following the instructions above I have successfully installed DW CC 2014 on my PC (windows 7) and installed all extensions including the server deprecated behaviours panels.
I don't know whether you need both CC and 2014 installed. At the moment I have both and have no intention of removing CC. I expect when the time comes to re-install windows 7 I will then only install 2014. but that's for the future.