It may not even be the vision they have for Automattic ... but I do think it's an opportunity they have.
For Gravatar, no it's not a social network at all, but it's a potential part of a bigger, wider identity platform.
If we're just discussing Automattic becoming a closed Facebook competitor, sure it's possible. I think they have the position to do so, but I'm certainly not interested in another closed platform, even if bits of the core software are free.
Gravatar is a wider identity platform, but it too just piggy backs on email. It's an avatar platform that piggy-backs on the email identity platform. And sadly, the avatar platform isn't distributed either.
In my opinion, BrowserID has a much better chance of being the technical and featureful identity provider. Anyone can be a BrowserID provider and provide any level of security from literally none to quadruple factor auth with PKI if they wanted. I would love to see proposals on how to layer functionality like Gravatar on top.
That's a social network alternative that I could get excited about!