Personally, I see Molly dropping the Winter Lady's mantle altogether and taking over Dresden's business after he retires. Odin gave Harry a pretty big clue about swapping mantles around or leaving them behind at the end of Cold Days, and while I think it's intended to be a Chekhov's Gun for getting out of the Knighting business, I think it can also apply to Molly.
I personally also think that the Fae Courts will be gone by the end of the BAT anyway, because Winter won't have to man the Gates anymore, so the mantle might simply change enough that Molly gets to still be Molly.
