What you're saying has nothing to do with what I said. I will concede, however, that I missed the bitstream license, which grants some protection to independent implementations. But as others have said, that is no guarantee.
Are you referring to this: You're covered unless Google decides they don't want to license one patent claim or another.?
Google is granting a license to all Google-owned and Google-acquired patents required by VP8. Google will be the largest user of VP8, so it is in their interest to acquire or defeat any VP8-related patents that may be discovered.
http://www.webmproject.org/license/bitstream/