Szymanowski or Witold Lutoslawski. He's done it before, and there's no reason to think he wouldn't do it again. But as to what exactly he'll play, don't expect to know until shortly before the concert. Zimerman is famous for not revealing his programs. Still, given his history, we can take it on faith it'll be interesting.
A better question is, how will he play it? At the peak of his powers, the fifty-year-old has the technique to play anything any way he wants. Since he won first prize at the 1975 Chopin Competition, Zimerman has demonstrated a stupendous technique, a soulful sensitivity, and a willingness to play fast and loose with tempos, all uniquely his own. And as his series of recordings for Deutsche Grammophon proves, Zimerman's individuality has only grown with the years.
There's his tone clear, bright, warm, deep, subtle, and always absolutely lucid; everything in the music is in Zimerman's tone. There's his line the way he shapes phrases and sculpts melodies, the way he pushes forward in developments, pulls back at climaxes, and achieves the still point of radiant silence in codas. But above all there's his tempo daring, even reckless, in its supple strength and forceful yet supremely graceful in its passionate impetuosity. Zimerman's heroes are said to be Claudio Arrau, Arturo Benedetti Michelangeli, and Sviatoslav Richter the three greatest pianists of the second half of the twentieth century and many hear their heir when he plays.