Thanks for the link..
He says his role is very short, I think it is just one scene..of him in the magic shop and doing a few tricks and then done with the movie.
Interesting how he still says he wants to learn directing process even though he says he's done with directing ?
If he gets to use his old song, I think Twilight Chapter Seven or Enchanting Melody would be fitting. I prefer Twilight. Hopefully they use it when Jay appears in the movie.
He'd probably use Mr Magic. Those other 2 songs have nothing to do with magic.
He already dismissed Mr Magic in the interview because it was too humourous/happy, while the movie has a pretty serious tone. Remember in The Era concert he had clowns dancing around while singing that song.
Enchanting Melody has themes of illusion in it. Twilight evokes mysterious feelings and based on detectives, which could sort of be loosely categorised into magic.
I don't think he will really get to write a new song for it, it's not common for Hollywood to do that (I think). Hopefully John Chu is Jay's fan and will try to put a Jay song in it. I don't have high hopes though.