I gave this more thought. You can't actually allow the user to update their email like this, since you're not verifying their new email. There's two scenarios:

1. The user mistypes their email address and logs out. Now they're locked out permanently, since they can't register the mistyped email address with Persona because they don't get the verification email.
2. The user changes their email address to one they don't own. Now they can do things on behalf of an identity that is not theirs. All of a sudden, `barackobama@whitehouse.gov` is playing Flappy Bird with a high score of 3.

There's a really expansive bug on changing emails using Persona that I'm sure @cvan can link you to.