You see, the problem with harem manga is that it's such an overused trope that you already know what will happen. And I assure you he will not end up with Ruka. It's either Nagi end or open-ended without anyone winning. Like Trash Taste Podcast said, if you read one harem manga, you basically read all of them. So seeing this development didn't make happy or excited, but rather sad and afraid because it'll never happen. They might end up together, but it's only gonna be temporary, like with A-tan, or not cause Hata is usually unpredictable.
What I'm interested though is what Ruka said at the end.