Highly doubt it's her son. I mentioned that idea to just say I have no clue what his role will be in relation to Shaw. Brother, it's possible. Son - maybe if an Engineer and Shaw get it on, or in another way, somehow she's exposed to more of the Engineer's "bio-former" and it somehow restarts her fertility cycle?
Another thought - there are very strong biblical symbols throughout Prometheus, what if Shaw represents the virgin Mary? She is given the ability to procreate by God (ie. in this case the Engineers) and ends up having a child who is part Human part Engineer, and somehow, has some important role in stopping the evil which was awakened on LV223 - Deacon perhaps?
I dunno, it's a far out there idea and I know how much everyone loved the "Jesus was an Engineer" theory, haha.
Again, who knows. Hopefully we'll have more to go by soon.