
Definitely hope there's more.
Some people find the seme's aggressive nature later to be off putting but I find that it rather fits well since before he was gentle and that made it seem like there's was a small distance (as Tora noted on pg 12.) I don't think he was extremely aggressive but enough to seriously prove to Tora that he wanted him

i feel that he is rather tamed for an aggressive person...

Yeah people who say he's aggressive have clearly never had themselves to deal with an extremely indecisive person (I'm like that so I understand Tora, but I also know it drives some people nuts).

Only now have I realized that Hayashida and Natsuo were in a relationship with each other before their current partners in their stories...

They weren't in a relationship. Hayashida was in a relationship with someone else called Yumi. That's who is smiling in the picture with him. You can find their story in Azami and Sabita Yoru.
http://www.mangago.zone/read-manga/azami/
http://www.mangago.zone/read-manga/sabita_yoru_demo_koi_wa_sasayaku/
Honestly I'm shocked with Hinata because I'm like, Hinata you can't do that, and Hinata, that's so like you and I smile. But I think that Tsukishima and Kageyama were chosen because they're are growing to provide foundational support to the team whereas Hinata is still trying to prove himself. Or that their mindset has always been what can I do to hold the team together. I'm not saying Hinata doesn't think like that but he's in his own mindset most of the time.
Of course their roles are also pretty much team oriented but even Ushiwaka thought about how being ace was a foundation for his team