Ones I’d like to see that make sense in lore and not because “Lawl battle pet droods be dorble squee!!!”? Thought ya’d never ask!
The way I see it with current lore the only race class combos left are
Night elf paladin: legion paladin class story
Worgen paladin: hearthstone sheds some light on this, plus the playable faction of worgen are light worshippers technically.
Kul Tiran paladin: though not as prevalent, some Kul tirans worship the light as well
Worgen monk: if an undead can achieve inner peace, why not a worgen?
Draenei rogue: if a race can be a hunter, they can be sneaky, hooves or not (actual hunting not pet taming hunting)
Lightforged Monks: I highly doubt they can’t achieve inner peace
Lightforged rogue: see draenei
Tauren rogue: the big meme, see Draenei rogue for my reasons why tauren should have this class
Highmountain rogue: see Tauren
Goblin monk: doubt greedy gobbos can’t find inner peace
Stretch classes:
Dwarf druid: this one comes more from the wildhammer who seem more in touch with nature, but it’s a bit of a stretch and likely to not happen
Tauren mage: with basically all their allies learning the ways of the arcane, don’t see why the Tauren wouldn’t dabble, again a bit of a stretch
Highmountain mage: see Tauren
That’s about it as far as I can see . . .