Yes, Google would be crazy to ignore good information and meta-data that is already there, but that doesn't change the fundamental problem:

People don't give a shit about metadata.

In terms of people writing metadata into pages by hand, then yes, I agree. But in terms of programatically generating this stuff from data that's already in a database or what-have-you, then I think it will see growing adoption.

The important thing here is to not commit the fallacy of the excluded middle... There's a place for the Semantic Web between "it's a total pipe dream and no part of it will ever come to fruition" and "it will be fully realized in exactly every detail as originally conceived by TBL."

People are already using Semantic Web technologies to some extent, the open question now is "just how prevalent will this stuff eventually become?"