I found this, is an interview from the recent Fanbook:
1. "The relationship between Soma and Erina."
> Actually in the final epilogue of Le Dessert, Tsukuda wanted Soma and Erina to get married. However he couldn't fit it into the storyboard so in the end he's decided that it's still too early for them to take that stage.
2. In the anime "Macross", there's a character called Basara Nekki who only thought about Music and the people around him were crazy about his music. When Saeki told him, "Isn't that kind of feeling really good?" Tsukuda considered whether he should give that kind of ending to Soma.
> But he's well aware that after 315 chapters and three extra epilogues, if Soma x Erina's relationship never progressed the readers would get mad and saying something like "Geez, Soma doesn't have guts!" "Come on, just realize your feeling and do something about your love life!"
So Tsukuda did some romantic progress by making Soma realized his feeling and made an oath to Erina in his heart.
3. Hayama
> Hayama is the only character who got married. Soma and Erina's relationship (the context is that eventually they will end up marry each other only Tsukuda didn't want to explain how) and the future of their friends is up to our imagination.
> The fanbook showed that the characters who are confirmed having love interests are Soma, Erina, Shinomiya, Mizuhara, Hayama and Hinako. It never exactly stated who Hayama's wife is but based on Hayama gossip section in the fanbook it most likely to be Jun.
>5. Mizuhara also used to have a crush on Shinomiya in high school
6. Souma's Scar Flashback
> The nine pages in the fanbook is about the flashback of Soma's scar when he was still a little child and Erina showed up at the end in her limo.
> Erina passed the shopping district in her limo and suddenly feel a sinister aura coming from that place. She said to herself, "it feels like someone from here will piss me off a lot in the future"
7. Asahi
> Tsukuda received a lot of letters from the readers asking who Soma would end up with. So the author decided to add Asahi into the story to make Soma realize his feeling to Erina.
> The scene where the girls gathered together in Polar Star talking about Erina's ideal type is the editor's idea to make her awares of romance.
8. Soumegu and Ryoalice
> There's a reason why Tsukuda made a lot of duos and made them always stick together (he gave the example of Soma/Megumi and Ryo/Alice) in the series, it's because he needed a third party to illustrate the shokugeki. He never intended for them to become couples.
9. Souma Traveling
> Although Soma has reached his goal to surpass his father, he went abroad to further his study. To serve the one and only person he wanted to dedicate his food to, he set off to achieve those new incredible tastes and continue his travelling in the endless wilderness."