Guaranteed non duplicates for duplicates and runes would be the worst they could possibly do if they want to earn money with this game.
More likely that we will get new card packs for them.
Naw I don't think it is conducive to whales to allow any sort of guaranteed gain.
Best they would do is introduce stuff like MPQ's "vaults" where if you clear out the entire vault you can get that mythic.
Remember pricing is for whales.
For normal user, you are supposed to think the money spent to benefit gained is terrible.