Eveyone

Pretty sure its either Erina, Megumi and Ikumi. Maybe also Hisako and Alice.

Alice i think has more of a thing for ryo she just doesnt realize it, id say Ikumi is the only one whos really shown a heavy romantic interest in him ever since she got beat... Megumi seems to like him as a best friend and as a mentor by the time the anime ends, maybe more by the moon festival but she could just really want to support her friend and keep him from getting expelled... And Erina is just barely getting past being able to be around him without getting pissed in the 3rd season .... My thoughts from anime only, havent read the manga

I dont think that there is going to be something like that because the anime focuses on Cooking and whats going on with the place etc. havent read manga yeat but i think if thats going to happen its prob in last season or something like that. dont know thats only my opinion.

There'll be spoilers in my answer.

Anyway, I'm updated in the anime and manga but if I stated something wrong, please feel free to correct me. I'm not that good in remembering things. XD 

The ones that are confirmed who loves Soma (as more than a friend, of course) are Ikumi and Megumi. Erina will soon realize that she loves Soma too as stated by the author. 

Hisako is still debatable but I truly think that she only sees Soma as a friend. 

Alice, on the other hand, is being hinted that she has feelings for Ryo.

I find Megumi and Souma's bond more like a brother-sister bond where a younger sister learns new things from the elder one. And I don't think they have any future.

Souma is reserved for Erina and that is why I feel sad for Nikumi :(((((

I don't know if this helps, but there is a blog on the subject Souma's possible love interest.

http://shokugekinosoma.wikia.com/wiki/User_blog:MCN51FJ/Soma%27s_Possible_Harem%3F