Naruto is not called "The Story of Sasuke and His Eye" and it doesn't stop the latter from being apparently a lot more important in the story than the guy the story is named after.
Hikaru wasn't going anywhere anytime soon. The people who see *potential* in him really saw Sai. If there was no Sai and he decided to play Go anyway, he'd be like a slightly more powerful version of one of the many pretty faces who turned out to be completely useless when matched up against anyone of any significance. Maybe people will pay for more attention to him since he's Akira's lover, err, rival, but then to be a rival might require you actually beating the guy once in a formal situation. Then again, in manga a rival really means a guy you clownstomped 999 out of 1000 times. Hikaru was not even the second most popular character of the series. After Sai left they literally have to invent new people just to have people bad enough that are relevent to Hikaru's skill level.
I mean you sure don't see Ogata or Toyo want to play Akira for a challenge let alone Hikaru.
Yes I know they had a scene where Ogata clownstomped Akira and then said it was actually like really, really hard and he was a worthy opponent, kind of like how a sports team will talk about their opponent played with their heart after owning them 4-0 in a series.