it's from a scan from 2ch from an interview with the author for www.entermix.jp
He actual said that he was hesitant between Hinata and Sakura for a period, he decided then for Hinata for long time. That suggests Kishimoto never thought to her about the endgame since the beginning of the story. He actually decided to choose her in a certain point of the story. My guess: or after Hinata's confession or after chapter 615 (and volume 64).
It's simple.
Wow... Well, if it's indeed true, then I literally lost all respect towards him.