This is a classic misunderstanding of Oreimo's ending. Kyousuke actually *does* end up with Kirino. Permanently. Earlier in the series, Kyousuke and Kirino make a bet which Kyousuke wins, and he wins '1 wish' that Kirino cannot say no to. In the ending, he ends up using that wish in order to break the promise that they'll only date till graduation, making them lovers into the future.
