Quote Originally Posted by EusisLandale View Post
No way to know until it's actually up, but if you've at least still got the clear save it's possible maybe. If it's gone? Not likely at all. The only way it'd happen otherwise is if there's been something hidden away tracking that stuff from the start.
Even in that case, achievements were never rectroactively given. The progression bar might be full but one needs to perform one more time the requirement for the achievement to be unlocked.

For instance, when HW was released, new dungeon completion achievements were unlocked. A lot of people already had run so many dungeons that they should have got them. However, they earned these achievements only after running their first dungeon post-HW release (mostly Dusk Vigil).