I think out of the three,
Edith is most likely to make a comeback. The other two both have strong associations with images of old women, while
Edith hasn't been affected by that. Also, "
Edie" is a common nickname for
Edith, and that isn't old-fashioned at all.
For
Agatha and
Agnes... I don't think they'll come back. I have seen a baby
Agatha recently, though.