Well i think you have to wait at least 3-5 months until katana comes, pretty much. So don't try to rush on it, nobody knows how long it takes. Just start your some other character, grind it, get gold and so on, so you can be ready for it when it comes.
And isnt those necromancer, rapier whatever classes just somehow datamined from their data, which is just like "beginning" data that its not 100% sure yet will they make it real, or will they start something completely new. Well if TW doesn't have in lockout necromancer, guess you can pretty much say that its not sure will it be next, or will they even make new class for while. All we can do is guess. :<