Hm, I have a few points to add to this since I have been reading up on Japanese news articles about this exact issue (or phenomenon?) that has some very interesting points that can be brought up that relates to this post as well as anime/manga in general. This topic has piqued my interest since Yuri!!! On Ice became so popular and focused on characters that were more or less viewed as not heterosexual and how it became such a hit, not only in Japan but around the world as well.
For reference, I’ve been looking at articles about Shonen Jump readership demographics. You can find the articles here:
Recent Poll taken in 2017, PDF version
Poll taken in 2012
Commentary on Fujoshi Culture and Shonen Jump
News Commentary on Viewership and the Strength of Women for Jump Manga
Basically what is happening in this day and age in Japan is that more youth want more solid representation, particularly focusing on the strength of women roles in pop culture.
Among the poll taken in 2012 between men and women for readership, almost 50% of all readers for the weekly Shonen Jump were women, and most of the series that women were interested included titles such as Haikyuu!!, Kuroko no Basket, Gintama, Katekyo Hitman Reborn, etc. while men focused more on Dragon Ball, Naruto, Niseikoi, etc. Of course these titles have changed over the years, but the fact that the demographic is almost half and half has not changed much for Weekly Shonen Jump.
In the more recent poll taken in 2017, although the poll deliberately left out the men/women demographics for the Weekly Shonen Jump, other Shonen Jump titles (e.g. Young Jump, Ultra Jump, etc.) had demographics of around 70%~80% male versus female readers. You might think, “Oh, but that means that Shonen Jump is still primarily targeted for males;” however, that might not be the case.
The commentary on the Weekly Shonen Jump demographics being deliberately left out, which are mostly men who were commenting in the threads, were saying that Weekly Shonen Jump is purposely changing to cater to the tastes of women instead of “young boys,” which is what it was originally targeting way back in the 70s. Some comments mention how women, particularly “fujoshi,” are influencing the way and direction that various titles in Shonen Jump (I’m pretty sure you can guess which titles they are, aka Boku No Hero Academia, Haikyuu!!, Kuroko No Basket, etc.) are adopting to cater to their main target audience. Also, other commentary in the thread include how Shonen Jump is trying to now cater to broader audiences, particularly LGBT audiences.
The whole LGBT movement in Japan has seen great improvement since, say, 5-6 years ago, when the Nikkei Poll was taken in 2012. The current demographic of Japanese people who label themselves as LGBT (or LGBTQ) is roughly 10%, but the number might be more due to people not wanting to reveal to the public what their sexual orientation is. However, there is definitely a change of opinions on LGBT in Japan, for example various wards in Tokyo now allow same sex marriage, and even large companies are introducing the option of “other” when choosing from Male/Female when signing up for various things.
One of the articles I linked above is a direct commentary on fujoshi culture and LGBT influence in Shonen Jump. The article points out that ever since the popular series in Shonen Jump called Saint Seiya was serialized in 1985, which was one of the more influential series that started the Yaoi/BL movement, female readership for Shonen Jump has been rapidly increasing to the point that it is almost definite that series writers now take that into consideration when creating stories for the manga that gets written into Shonen Jump depending on the series (for example, the ones that clearly cater to females, such as Haikyuu!!, Kuroko no Basket, etc. that was mentioned in the 2012 Nikkei poll).
Further, judging by the amount of attendees at conventions in Japan such as Jump Festa, interestingly enough, a lot of the merchandise booths focus on goods for series that appeal more to WOMEN, such as Prince of Tennis, Boku No Hero Academia, Kuroko no Basket, Haikyuu!!, etc.
This is not to say that the series in Shonen Jump are all trying to cater to women or LGBT; however, the news article about the increasing readership of women with Shonen Jump and how it is affecting the Shonen Jump manga does provide interesting information.
The article starts by first listing stereotypes of women throughout the years, for example in the 70s, 80s, and how it has changed drastically in present times. Women are holding more positions of power (although Japan’s workforce for gender equality is still abysmal lol), but because of this change, a lot of women who do read Shonen Jump would like to see more strong female characters and/or would like to relate more to characters in the various series. More representation for females is not the only thing that Shonen Jump should focus on, which at this time and age, everyone wants at least some positive representation, including LGBT. This can lead to the publishers taking more chances to bring in more representation, and even Japanese male readers have noted the changing themes in specific Shonen Jump series (with many comments being that Shonen Jump is getting gayer and gayer lol), particularly the ones that have a stronger female readership.
I personally think that the industry knows what sells with who, and they will exploit that to fit their audience of choice. Authorial intent of course is important, but perhaps that is also taken into consideration along with other factors, primarily what generates cash is what they’ll bank on. In this case for series such as BNHA, Haikyuu!!, etc., they know what their main audience wants, and they’ll milk that as much as they can.
To be more specific, Horikoshi did mention that he would like to continue BNHA for many years to come. Perhaps in 10 years from now, having a canon main LGBT character is not uncommon at all. I mean, even Disney is thinking of making an LGBT princess, so hey, why not? I wouldn’t keep my hopes too high, but that is not to say I will not have that hope at all.
Anyway, that’s my own research and opinions on this, and of course this has no effect on what happens with the way Shonen Jump deals with representation, but it’s just some interesting food for thought.