Planeswalkers with good board control options and high loyalty counts are hard to deal with, much more so than cards like Elesh Norn or Griselbrand
Beyond those three, its anyones guess, but Ive been through the list of available mechanics and keywords to pick out what seems the most likely: Battlecry A Go Wide strategy is likely given the huge armies and battles in the series, and battlecry is a way to help break stalemates
While massive surges like that often don't last, this Arceus card continues to climb back up, though it should remain below $100 for the immediate future
Nothing at a low mana cost though, like blue, red, and even green have been getting
I have placed Fury third on my personal list because I think it has a lot of impact in the current Modern environment and may even continue to gain influence