Why? City dvelers need to eat, but they can't have many animals, so what would they eat? Maybe fruits, vegetables and berries, and who else is better at tending to plants than Sylvani? Also, lore wise Sylvani are already pretty keep on whole ancestors thing. Sylvari are only born from the pale tree. We know roughly the whereabouts of the firstborn and the sylvari that followed. There is no place lore wise for an entirely new floating city to the north to appear populated with sylvari. And yeah this sounds a lot like the revenant; could take some of the ideas and turn into an elite spec. I say that because I dont think anet will ever be adding a new profession to the game as they've gone the elite spec route which in my opinion is better.