So, to go back on the topic of speculation, I think these partner showcase show what partner are really important to Nintendo. The first partner showcase was mostly about Atlus. We already have Joker from in the first pass, maybe he was chosen to strengthen the relationship between Nintendo and Atlus. Considering this, the second showcase have a pretty big focus on Square games (Kingdom hearts, Final fantasy crystal chronicles and Collection of Saga). I know Square already have one character in the first pass, but maybe they would want another one to stregnthen that relation even more.
Another thing to note is how Namco is pushing more and more the Taiko franchise in the West, which isn't that surprising considering the success of Drum N fun, and Sega is pushing more and more Puyo puyo in the West too. I wouldn't be surprise if Arle or Donchan end up being a character.
Thoughts? Recently there's not a lot of things going on to speculate, but maybe these partner showcase is a good base.