Oreimo/WMG

The ticket to America wasn't what Kirino wanted to show Kyousuke as part of the last life counseling session.
Kirino tells him there's something else in her closet that was way in the back that Kyousuke didn't know about, and that she will finally show him because of everything else he saw in there. She opens her closet, but the box with her album in it falls out- she does not hand it over to him. The ticket may have just fallen out coincidentally. Who's to say that's that Kirino wanted to tell him?
 * It's actually revealed in the light novels, but the photo of young Kirino is a big part of it.

Kirino is bisexual.

 * Do I really need to explain this one?
 * Ahem. It's called wild mass guessing =P

Kirino has a crush on Kuroneko.
It seems that Kirino's way of dealing with affection, especially of taboo sort is to deal its target like dirt. See how similar her banter is with Kyousuke and Kuroneko, and she is shown to use her vitriolic attitude to cover up her affection and possible romantic feelings towards her brother. Wouldn't the other major target of the same attitude be possibly also be a target of similar hidden feelings?

The Akagi siblings will star in a Spin Off named "My Little Sister is Cute"
Less a WMG than speculation based on a comment in the Episode 13 DVD Commentary, which showed quite a nice dynamic between the two, and specifically teased a Spin Off with that name. I'll go a bit further and say that the DVD Commentary itself was a test case to see how the reaction is in the community--if it's positive, they get their own manga or something.

Kirino and Kyousuke are Not Blood Siblings, and the proof is in that album she was going to show him
This has already been teased in an If route of the PSP Visual Novel. It's been mentioned on different forums that with the current climate in the wake of the recent anime content bans, the only practical way to end the story would be either an ambiguous ending like the Episode 12 Good End, Kyousuke ending up with one of the other girls (which can never be ruled out as a possibility, but seems unlikely considering how Volume 8 ended), or Kyousuke and Kirino ending up unrelated and starting a romantic relationship. It's already been shown that, although the PSP game isn't canon, it has foreshadowed developments in the Light Novel, like. They've already shown pictures of Kirino and Kyousuke as very young children in a few of the anime's openings, which directly contradicts the If route. However, this doesn't rule out the possibility of Kyousuke having been adopted before Kirino was born, and the album may have something like Kyousuke being nursed by his real mother to prove it.

This is another universe that Haruhi Suzumiya made.
One day a certain Reality Warper said "You know, my life is great and all, but what I'd REALLY like is a world where I was in some sort of incest love." So she destroyed that world and made this one, where she's on the fence about liking her brother. In this world, Kirino is Haruhi, Kyousuke is Kyon, Kuroneko is Yuki, Manami is Mikuru, and Saori is Itsuki.