I still think Zach is back. No inside info, just a hunch.
Next year I think he will be used slightly different in a way that will benefit his NBA stock and the Purdue team as a whole. Other guys like Loyer, Smith, Kaufman, or Colvin might see an uptick in shots while his usage getting post touches might go down a bit. Purdue will be better for this in March.
His rebounding will still be elite and I think we'll see another jump in defensive improvement in rim protection and agility that the NBA needs to see growth in. He's gotten progressively better defensively every year. Maybe he'll get the green light to let some jumpers fly on pick and pops if he keeps working on that area too.
Zach seems like he bets on himself and the work he puts in and next year he'll be in a better position to get drafted with his continued year to year progression even if he doesn't sweep the POY awards again. He's a year young for his grade and has still only been playing basketball for a short period of time.