Er, Arya spoilers below.
For all we know she'll be mucking around in Braavos forever, much like Dany in Slaver's bay. The place she's at never says anything about faceless men and none of them show the face swapping powers. I always found it kind of weird how she just stumbles into the supposed training ground of the faceless men and learns to become one. Her character is pretty interesting there though, how she employs her blind vengeance and is punished for it.