IMO, I think Blizz will print 1-2 unique strong class cards for Warlock / Mage / Priest that they could use for their highlander decks.
These cards will have nothing to do with "No duplicate in your deck" but they could be strong enough to make up the individual disadvantages that Mage / Priest / Warlock run in their highlander decks.
For Warlock, there could be a Rare / Epic card that will restore your Hero's health for double the amount of time you use Hero Power in this game.
For Mage, it could be a spell that gains Armor as many as double the enemy minions that you destroyed in this game.
IMO, I think Blizz will print 1-2 unique strong class cards for Warlock / Mage / Priest that they could use for their highlander decks.
These cards will have nothing to do with "No duplicate in your deck" but they could be strong enough to make up the individual disadvantages that Mage / Priest / Warlock run in their highlander decks.
For Warlock, there could be a Rare / Epic card that will restore your Hero's health for double the amount of time you use Hero Power in this game.
For Mage, it could be a spell that gains Armor as many as double the enemy minions that you destroyed in this game.
For Priest, it could a minion that can Discover a class card that has Healing effect: Priest of the Feast, Greater Healing Potion, Flash Heal or Darkshire Alchemist, etc.
I believe that there is tons of ideas out there to help future Highlander decks to exist without Reno.