It's possible that it will be added, but from the looks of things, the main point of co-op is to teach new players the ropes of the game and stats would be at best unnecessary and at worst misleading.
In order to make the co-op stats viable, they'd have to be ring-fenced so as to not affect the other player averages, and from there it just becomes a pet project. Co-op was useful, but to be honest I don't think I'll go back to it now that I kind of get the game.