Exactly, I don't see how that is vague at all. It is so blatantly obvious that it is going to be Devil Summoner 2 that they might as well not have bothered dropping a clue like that.
Even if you didn't recognise the silhouette, the SMT logo gives it away. Do you know any other Shin Megami games in the pipeline right now?
Unless it was a brand new Atlus USA developed title, it's gotta be something that's already been released in Japan and Atlus USA is hinting at its localization here.
Which leaves us with just Devil Summoner 2.
Like some have said though, the only question is whether we'll get the Maniacs Chronicle edition of Nocturne, and I think there's a good chance we will, considering it's just a few changes to the dialogue (replacing Dante's lines with Raidou's).
Though I do wonder if Atlus USA will release it as a separate game instead..