So caught up in Ninokuni was I that I missed out on some important Layton news that came out in the Level 5 panel Q&A: Akihiro Hino says Diabolical Box is on its way to the US.
This is the logical conclusion for the second game in the Professor Layton series — it sold like hotcakes in Japan and Curious Village did pretty decently stateside as well. But, now that the head man at Level 5 has said so, let it be known as true: Professor Layton and the Diabolical Box are going to the US "in the next six months."
Currently there are four out in Japan plus one "friendly version" of the first game and a special edition of the second game. Hino said during the main part of the lecture that he wants all six of the Layton games to come to the US and Europe.
Cheers to Rebochan for cluing me in; I had to duck out of the Level 5 Q&A to make it to that God of War III panel.