There is an interesting pattern with the relationships you mention. Outside of Minato/Kushina, they are romances without any romance. Kishimoto doesn't care much for showing you how the couple formed. Just that they did. You don't see much outside of some hints, and then it is confirmed in a few panels. To him, the bonds of friendship are more important. The exception is Minato and Kushina since their love was their bond and it was vital to Naruto's story.
Yahiko-Konan: Nothing hinted at them having interest in each other until that one flashback panel with them about to kiss and Nagato smiling as he left them alone.
Jiraiya-Tsunade: We didn't learn at their regret over not hooking up until the time of Jiraiya's death.
Asuma-Kurenai: Zero hints of any romance except for Kakashi believing they were on a date, which they both denied. Then start of Shippuden and we learn they got married and Kurenai is pregnant. Interesting that Asuma never was shown with Kurenai in Shippuden once. His relationship with Shikamaru was more important.
I don't know how any of this plays with NaruSaku. It could mean nothing. But I think it shows Kishi isn't as interested in showing the development of a couple. Choji could end up with Ino with almost no development. ShikaTema has way more development than AsuKure did and is basically a carbon copy. Neji and Tenten could be together with no development. So it does make me afraid that NaruHina and SasuSaku can happen, even with their lack of development. The "epilogue" might be where everything happens.
Edited by Deej, 18 February 2012 - 11:37 PM.