Moffat said something on Doctor Who Series 9.

“You’ve got Jenna onboard for another series, now one of the longest serving new series companions. What are you doing with Clara this series? What’s her journey this series? Oh, it’s very pronounced. I mean, I can’t really say too much about it, but, you know, she continues to complicate, as it were. And that relationship between the two of them is incredibly strong. Very, very strong.”

Things that make me go hmm, especially with what Jenna said earlier…

“It’s really interesting where it will take them next… it’s a direction that no-one was expecting.”

I predict gnashing of teeth, and the lamentation of their women from some portion of the fandom.

This goes two ways, either of which are plausible. Either a) Clara becomes and opponent to the Doctor, or b) their relationship takes a…May-December quality.