Miracle was already pretty dead. Watching Forsen and Hyped play it on stream, arguably two of the best Miracle Rogue players, they were still losing quite a bit. Over 50% I think. You haven't seen it in tournaments lately either. Loatheb and Sludge Belcher wounded it, this is a nail in the coffin. Rogue has some great cards, there has to be something out there that'll be good. Malygod, maybe Alex-Miracle done a little differently, but the current Miracle deck is dead imo.
So it looks like Druid, Priest, Warrior, Warlock will at the top after the change and maybe Shaman. That, to me, means Mages might be viable again without Hunter around. Be a nice bump for them since they are the worst ladder class right now. Hunters will probably go back to non-beast face rush decks which won't have a favorable win rate vs Warrior, Priest, or Druid. So Rogue and Paladin are the two classes that I'll be looking at for a new deck innovation to see if the meta can be shaken up.