Although this reveal didn't feature in the main trailer, the new song dropped alongside the announcement of Utada Hikaru's new theme for the game.
At the end of 0.2 Birth By Sleep, it was revealed that both Riku and Mickey would be receiving new outfits to combat the darkness. We finally get to see them here, and they're surprisingly similar to Sora's own outfit.
This section of the trailer also revealed to us that Mickey and Riku will be returning to the realm of darkness, presumably to look for Aqua and recruit her for the cause. How exactly did they get here?
It also shows that Riku's Way To The Dawn Keyblade has been broken at the blade, which he doesn't seem too fussed about. He buries it in the sand and states that he's leaving it for his other self, which might be hinting at Riku having his own Nobody.
And yes, Riku does look a lot like Noctis, doesn't he?