According to iMDB, the Doctor's new companion (played by Jenna-Louise Colman):
I. Have. SOOOO. Many. Thoughts.
a.) This is Rose's little sister because Jackie was pregnant the last time we saw her. At Bad Wolf Bay in Doomsday Rose said so.
b.) It's almost too much and too awkward to think that this could sorta possibly be the Doctor's daughter. Y'know, Rose and clone of the Doctor's kid.
c.) This one's my favorite thought so far. It's crazy, but it ties everything together in crazy wibbly-wobbly timey-wimey-ness. The Doctor, in the original series had a granddaughter named Susan Foreman. Okay, so different last name, but that could be made up for in so many ways, plus, have we ever heard of Time Lords actually having a last name? It could have been something she picked up like the Doctor's John Smith to hide her identity if she ever crossed paths with Rose.
Think about it, "Silence will fall when the question is asked...The first question. The oldest question in the universe, hidden in plain sight...Doctor who?" And who, other than the Doctor and River Song would know the Doctor's name? His granddaughter Susan!
d.) She has nothing to do with Rose and Steven Moffat is just messing with our heads again.
e.) It's iMDB and it's as reliable as Wikipedia until it's confirmed.