it would be better if the developer of pokemon go will include bitcoin to purchase candy credits in game, also have btc exchange system that will allow user to user trade pokemon, items using bitcoin *crossfinger.
I think the purchase candy credit with bitcoin could still happen if the dev pokemon adopt bitcoin as a payment system. But to provide a marketplace selling pokemon with bitcoin I think it's a little weird, different if there is a forum gathering place for fans of this game. And here we can purchase pokemon account, as happened in this forum.