It depends on the plugin. Some would allow you to just move them to a new folder but others will require a new installation if you wanted them in a new folder. The reason is that the activation of the plugins requires them to be in the installed folder so that they function correctly.
You can also leave them in their current folder and point each application to the folder their currently installed in through the additional plugins option so you don't have to move anything but will still be able to use the plugins.
Sorry, but Photoshop CC no longer has an additional plugins folder option.
That's correct. When we moved the standard set of plugins that are installed with Photoshop into a new location, we removed the additional plugins folder option. The traditional "Plug-Ins" folder is now reserved for third party and optional plugins (you should see this folder next to the application, but it is initially empty).
Generally speaking, you should be able to just copy or move your third party/optional plugins from Photoshop CS6 to Photoshop CC, and they should just work. There may be exceptions (e.g. licensing requirements) that will necessitate a re-install, but for most cases that should not be necessary.