Yes they will… Once the trial expires, the product removes user access to the Work Folders and so your clients will no longer be able to gain access to the work files stored within their Work Folders (until such time as the product is registered and user access to the Work Folders is once again restored).

Further, when the product is uninstalled (via the “APPLICATIONS” page in the server Dashboard), it will reverse everything and put the server back to the exact state it was in before the product was installed (i.e. the Work Folders functionality will be completely removed from the server). Of course, any user data stored within the file storage location will be left 100% intact over on the server just as you’d expect it to be (but the clients will simply not have access to it).