Hello Scott,
thank you very much for your answer. I was a little bit confused about this question, because there are some bloggers who claimed that VMDirectPath and USB Passthrough are supported for vMotion since the release of vSphere 4.1
http://blogs.virtualizationadmin.com/lowe/2010/07/31/naming-and-vmotion-changes-in-vsphere-41/
http://www.virtualserverguy.com/blog/2010/8/19/vmotion-changes-in-vsphere-41.html
but I was unable to prove this in the official VMware documentation.