I must disagree somewhat with @yogesh
In general, never manually copy files across from older Plugins folders…
BUT…
As far as we know ALL extensions/plugins which worked OK in v2015 should also work in v2016.
HOWEVER, if you do NOT have the Preferences > Extensions Policy set to ‘Uncertified’, most of them will NOT load/work - BECAUSE very few have been ‘signed’ for full v2016 load-ability [thus far].
You can also not be assured that this ‘Unrestricted’ policy will always exist - so get ‘signed’ RBZs whenever available.
If you install from the EWH their RBZs should still install, load and work.
Because most of these are still unsigned they will probably be marked as potentially incompatible, so you might be forced into doing this process individually.
RBZ files which are only available from SketchUcation’s PluginStore can also be installed into v2016 and should load with similar success. However, the PluginStore [or the testing ExtensionStore3] has a ‘Bundles’ function, so provided that you have previously used to tool in v2015, it will give you a list of PluginStore files installed of that, and you can use that to AutoInstall those into v2016 - you can also edit the Bundle to install just what you’d like to go into v2016…
In the SCF PluginStore you will already find several signed RBZs already available for download/install - including the new ExtensionStore3 itself, all of Fredo’s tools and his required Lib, and several of my own plugins and so on…
More will follow shortly - but there is no immediate panic because running in ‘Unrestricted’ policy they all should work anyway.
BUT, the proverbial WILL undoubtedly hit the fan is that policy is eventually phased out, after which only ‘signed’ files will load…