Correctly licensed files on "shared"/"wts" should be transferred to Commons. This is a process that's best organized by the community as licenses have to be vetted, templates adapted, etc. If a file is uploaded to Commons under the same name under which it was previously uploaded to WV, then it should "just work". If it needs to be renamed to avoid naming conflicts on Commons, then pointers to it will have to change as well.
Is there any way to retain the file history when transferring files to Commons? And will it be okay to list as the "source" of the file a link to a site that will no longer exist?
As has been noted, non-free media can only be uploaded locally, and only if a wiki has an "exemption doctrine policy" as per the WMF licensing policy:
Do we need to get the EDP approved by WMF? And if so, how do we do that?
Powers &8^]