Squinting at that small poster it looks as if it's a grown up version of Apollo and Silvia. But I'm wondering how that connects to the end of the first season (or maybe they'll just not give a damn about it
)
Although it's possible they'll go into Apollonius and Celiane's story since it's more relevant to the title: "Uragiri no Tsubasa" (Wings of Betrayal)...
But when I see that pic on the official blog with those genga papers, it looks more like Silvia than anything. Unless it's Celiane before she had a haircut.