The Sally cycle hasn't turned enough yet. If it's a name associated with our age group, or our parents' age group (Beverley, Patricia, Janet, Anne, Barbara, Shirley, Margaret, etc, etc) then it's out for us. It has to be our grandparents or further back.
tunaday, I have to say, I really disagree with your thoughts on Lily. It's easy to say Tracey and Dawn sound dated because they have gone through their fashionable stage, exited it and now sound tired and dull.
Whereas Lily is still widely used, it's hard to imagine for some that one day it will reach that stage, too. Everyone has agreed that it'll go through peaks and troughs of use (it's doing that right now), but because it is is being so widely used right now, it is bound to fall from fashion, as anything fashionable inevitably does in the search for the new big thing. :)
I think in a generation's time it will be very easy to pick a Lily's age!
It will be a 'Mum' name then and everyone will be avoiding it because tastes have moved on and yes, it will sound dated.
I keep referring back to my own name, which is a very old name going through a massive resurgence right now - but was massively dated when I was given it in the 70s. Just because a name is old, doesn't prevent it from joining the ranks of cyclical names.