So, the person Gwen has her affair with (Oh, poor poor Rhys. *huggles him*) will be... Owen.
Yes, that Owen.
And I just have to say... so called it. Jack/Gwen as the decoy for another ship, and we knew Gwen would have an affair, and as cool as it would have been, I doubted we'd get an affair with Tosh. And after what went down in The Ghost Machine... there's a shared experience.
But, was right on my decoy theory. And yay for me calling things correctly.
That said, after the squee of having worked things out. I have to consider it more. Namely: Owen might be a nasty twat, but he's interesting. And the affair has the potential to be very interesting - and, it won't be the Doctor vs Mickey thing Rose had going. It's the relationship she really shouldn't be having, and Owen mightn't come out of it at all well.
It has the potential for some very interesting character stuffs. In the "It's all going to go to hell" way. Not a nice ship at all, but one that has interesting dramatic potential.