If I had to guess, the mobile app is just a small part of a MUCH bigger Gravatar pivot. We've been seeing hints of this for quite a while with the hovercards, linking websites to your account, etc.

Keep in mind, Gravatar is not just a WordPress thing. It's also been adopted by other very large sites like GitHub, BitBucket, StackOverflow, and others. I realize those are kinda tech-oriented sites, but hear me out...

Could you imagine if you could "follow" Gravatar users and keep track of their activity across the massive network of Gravatar-enabled sites? We've all been participating in what may be one of the larger social networks on the web without even realizing it.

Disqus has been attempting to do something similar, although that's just for comments. Gravatar can potentially track your GitHub commits, blog comments, blog posts you author, etc. And Disqus actually has the option to use a Gravatar for your avatar picture too.

It's hard to say if this was Automattic's vision since they acquired Gravatar back in 2007, but I think Toni has recognized potential to be much bigger than just a "globally recognized avatar" service, and he's acting on it.