I like a good incest story as much as the next person (hell, I just wrote a 10 page paper for school about how there's no reason for incest to remain taboo), but I never saw the possibility of an incest end for this series. I think Kirino set the record straight in the first novel: the idea of 3D incest disgusted her.
I see her behaviour towards Kyousuke as merely a sister desperate for her brother's attention. Though she won't admit it she likes all the attention and consideration he gives her now and doesn't want to lose it. Check out the Kirino thread for my theory as to the cause.
I suppose you could still call her a bro-con and it may be a bit unhealthy but I don't think she has romantic feelings for Kyousuke. Even if she did, he certainly doesn't. This series was never marketed as a forbidden romance between siblings, but rather as two siblings reconnecting as family after being so distant. I have to wonder how people would view their relationship if Kirino's obsession wasn't incest eroge. That fact certainly polarized the series.
Spoiler for As for volume 7:
Anyone who didn't think Kirino's words at the end of volume 6 was leading to a faux-boyfriend senario, they fail at genre saavyness
That was obviously going to be the case the moment she said it.
I think the Kyousuke/Ruri twist at the end of volume 7 is an interesting development. I certainly approve of this pairing and it would be nice to see them last. Ruri doesn't seem the type to beat around the bush, so the moment she was sure of her feelings she took action to get what she wanted. Good on her.
Kyousuke's decision to go out with her is what I'm really curious about. I'm sure the next novel will elaborate on his decision, especially in the light of how he told Manami that he'd reject a girl who confessed to him because he wanted to keep things the way they were. But I suppose that's something that has change over time, as he seemed quite content with how things had changed for him.
Kirino definitely isn't going to take this sitting down, so it'll be interesting to see how she handles it, especially after this fake boyfriend business she subjected Kyousuke too. Though admittantly I care more about Manami's reaction. Poor girl