I think the locket is going to tie into his second vow of the Edgedancers in remembering the forgotten. Brandon has made such a point to letting us know that Dalinar has forgotten a lot about her, and that her sons still actively try to keep her memory alive.
It's a little foreshadowing (I could be grasping at straws), to the ED values when Renarin asks him if he "Remembered his mother's locket." Remember his Mother. Remember those who have been forgotten?
Perhaps later we'll see that through his memory of his Mother (and probably his murder of Sadeas, although I doubt he'll be forgotten), he'll be able to care more - making him more radiant.
The thought of him being Brave! and Obedient! seems so trope that I'd almost be surprised if Brandon went with this. Besides... Some Lift/Adolin dialogue has the makings to be awesome. Imagine the "I belong to the same order as THIS urchin?" conversations! Hah. I hope this happens. Adolin learning from a little girl how to use his powers would be hilarious. People think that just because we've seen one Edgedancer there can't be another. Let's not forget that Lift's "uniqueness" is probably going to come from introducing her Old Magic? (food->stormlight) skill to the other main characters. We all know how Brandon loves his magic systems to come in 3's. Also, Edgedancers are supposed to be amazing/graceful warriors. I dont see Lift learning how to utilize her skills along swordplay. She's a thief, not a warrior. So Adolin becoming ED would not necessarily be a redundant thing.