Here's a hot-off-the-press spoiler from Kristin from E! Online's newest chat:

I heard that the little girl seen this season on Grey's who felt no pain was supposed to turn out to be the daughter that Izzie put up for adoption. Any truth to this?
Funny. Do you think that rumor was started because the little girl was sort of a Claire from Heroes? Anyhoo, I had not heard that, and I also know that casting agents have been in Toronto recently, looking to cast a girl between the ages of 10 and 12 for an arc next season. Now, as much as a great show like Grey's might plan ahead, this seems to be way ahead, if you ask me. So, my first thought is that this girl is Izzie's bio-daughter.

So, will we finally get to see the daughter of whom was announced - then forgotten about - next season? And what would her story arc be? Will Izzie's daughter be wanting to come spend the next chapter of her life with her real mommy? Shonda can do no wrong.