I disagree. People are tired of leveling new races.People are tired of leveling new classes. This is why 4th specs are the best idea for everybody.
The biggest criticism to 4th specs is adding 12 new specs. Too much dev work to be feasible. A compromise would be 3 new specs that are shared across the existing classes according to the specs they lack. This would be the same dev effort as a new class, but greater depth to the class you already love.
Tank: Shaman, Warlock, Rogue, Priest
Ranged DPS: Paladin, Warrior, Monk, DK, DH
Healing: Mage, Hunter
These three roles can be based on any theme the expansion requires: Timewalkers, Shadowlands, Tinkers, Void, Light. Much more flexible than a single class that needs to represent a singular archetype. Also more fun and interesting to integrate what the new spec brings to the base abilities of the class.