If Return to Return to Mirrodin really the mid-late 2016 block, I hope they actually do something with the Praetors, especially Urabrask. The fat pack booklet made him seem integral to the plot, but the block novel didn't even mention him. Or any of the other praetors, for that matter. I read that shitty book on an airplane and still managed to feel like it wasted my time.
Still, the idea of red mana fucking up Urabrask's Phyrexian "programming" and causing him to turn against the other factions sounds like the right kind of cheesy sci-fi plot for Return to New Phyrexia. He's already taking in Mirran refugees and hasn't been killing or Compleating anyone, so something's up.
.... Then again, knowing the writing staff, I'm sure they'll start the plot with "lol Elesh Norn slaughtered every interesting character offscreen". Then Jace will show up riding on the back of an Eldrazi, brood for a bit, then hop off to make snarky comments at Karn.