I doubt it. The term "Tinker" is well known in the WoW community, and it's immediately recognizable as a term for Gnome or Goblin inventors who use technology to fight with. Even the Warcraft RPG used "Tinker" as a character class instead of Engineer.
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Problem is that Orcs and Draenei piloting mechs looks pretty dumb, and a Tinker class using every type of tech in the game would be unfocused. Classes should be focused, and the specs should be somewhat interrelated. While having Goblin tech in one spec, and Draenei tech in another spec sounds cool on paper, in reality it would be all over the place and kill the class fantasy.
Nah, engineering will be fine. In fact, I think that a tech class would actually increase the popularity of the profession.Tinker will destroy the Engineering profession's purpose and they can definitely not remove engineering altogether because a lot of people have paid tons of gold to get that shit up to max. And also, they've never done a new class after one another so I don't see it happening.