There seems to be an assumption that we won't see Jenna-Louise Coleman again until the Christmas special.
But the assumption until about 7:30pm on Saturday was that we wouldn't see Jenna-Louise Coleman until the Christmas special.
Moffat lies. He's famous for it. He'd rather lie than spoil a nice surprise.
That's all I'm saying. I have no insider information, not a sausage, but I'm predicting here and now that there's a good chance that she'll be back between now and September 29th. Whether as Oswin, or Clara, or someone else entirely, I don't know. But yeah, I reckon she'll be back sooner than we've been told.
(If I'm right: I called it! If I'm wrong...I'll have to delete this post...)