When the negotiations started, Brandish asked August where God Serena was. August simply replied, "He's here with me." Why didn't he just tell them Acnologia killed him? That got me thinking. He probably could've just meant that he will always carry him in his heart but there's two other possibilities.
- He resurrected him: Being the King of All Magics, I don't think it'd be too far fetched that August would know some kinda Necromancer Magic, or even Living Link Magic. And reviving the strongest Wizard Saint wouldn't be a bad idea. This is the guy that took out four Wizard Saints we're talking about. And if August resurrected him, we could see Natsu vs. G. Serena. And if the Salamander could defeat, or at least held his own against, the Hybrid Theory, that would show he has the potential of becoming a Wizard Saint, which I hope happens to him by the end of the series. Also, I love it when Natsu fights Dragon Slayers, and I feel Hiro killed off a Dragon Slayer he just introduced too early. And don't forget, we still haven't seen his other four Dragon Slayer Magics.
- He took his Magic power: Despite being the Magic King, August doesn't Dragon Slayer Magic. Otherwise, Acnologia would've attacked him after killing Goddy. If he took Goddy's Dragon Lacrimas and implanted them in himself, he'd be more killer than he already is. Then maybe Natsu or the Dragon King could fight the Magic King.
I'm hoping the first one happens. But I think the second one's more likely.