I have uninstalled the older version with no issues...
..maybe a few file association issues, but nothing serious.
This messages says (at least some) CC 2014 programs use NEW plugins https://forums.adobe.com/thread/1499663
-so do not uninstall the older CC programs if you use plugins in your programs until you are sure you have plugins that work in CC2014
If you are sure you don't need the old CC programs
-http://helpx.adobe.com/creative-cloud/help/install-apps.html to install or uninstall
-read reply #3 about the ORDER of uninstalling & installing https://forums.adobe.com/thread/1242671