Clearly reading by humans is impossible given the volume, but I don't think that's what Gregg Bell meant. Google is clearly going through emails and developing user profiles in order to target advertising. In that sense it is being read. I'm fairly confident that Google is storing those profiles, since the advertising seems to be taking prior messages into account.

Whether the content of those profiles is or is going to be used for purposes other than advertising is an open question. I'm fairly certain that Google can make a good sum of money if they decided to sell that data to third parties since everything from credit bureaus to employers could make use of at least some of that data.