Exclusive: Mindfulness to become the fourth circle to fill:

Continuing on the success of the activity, people familiar with the matter have informed me that Apple are thinking of implementing a Mindfulness goal into the Activity App.

This would not surprise me in the least, although Apple needs to make the Breath app better if they're going to have a ton more people doing it. Also, I'm hoping that this is added as an optional goal, much like standing is today. Not everyone is going to want to participate, and even those who do meditate may be offended by the idea of being asked to quantify their meditative time.