It made it into the final version.
If I understood it correctly then the reason it wasn't discussed by VMware employees at that time (and the notes disappeared) was because that the intel driver wasn't ready yet.
Anyways that was during the preview, the feature certainly did make it into the final version, see also https://pubs.vmware.com/Release_Notes/en/fusion/8/fusion-80-release-notes.html
Added USB 3.0 support to Windows 7 virtual machines (with the latest Intel USB driver)
cheers!
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Wil