Board Thread:Spoilers!/@comment-1916997-20171216041419/@comment-25375217-20180307184332

Going by the method of Dr. Sage's death and the current leading theory that she may be Yzma (granted, it's literally the only theory I heard, but y'know), she could be an alchemist/potion master. Blending things together to create magical brews. Sage is a spice and could be one of her ingredients. Alternatively, a sage is a wise person, so she could perhaps be able to see the future or read minds, or something else based on brain power and knowledge.

The Blind Witch is generally psychic powers, moving things with her mind (and Once used this for her in Season 1 and 5, too).

So we have plant-based magic, mediumship, alchemy/mind-reading, psychic powers, and basic witchiness (Regina/Drizella/Anastasia's jack of all trades, master of none shtick). I'd say whichever magic Dr. Sage has, the other still has a good chance of being featured through someone else. That leaves two forms of magic. We could maybe see more elemental magic like Gothel -- ice or fire seem most likely -- and maybe some species magic, like dragons, fairies, or mermaids.

Going by those different kinds of magic, here's my updated list:

The Snow Queen is more recognizable than Mother Trudy, but they've already done an entire Snow Queen arc so she seems less likely. And I don't know if they'd do the classic Arthurian villain or the Disney villain (considering Gothel, Leota, and Yzma are already Disney villains).
 * 1) Gothel - Control over nature
 * 2) Anastasia - Jack of all trades
 * 3) Madame Leota - Communication with and possible control over the dead
 * 4) Dr. Sage - Reading minds (not sure who her NEF counterpart would be)
 * 5) Blind Witch - Psychic powers
 * 6) Yzma - Potion brewing
 * 7) Snow Queen - Creating ice or Mother Trudy - Control over fire
 * 8) Morgan le Fay - Fairy magic or Madam Mim - Dragon magic/shapeshifting