Extreme love can turn to extreme hate pretty quickly under the 'right' conditions. Imagine if you make a move on Yumi and Chika walks in (or Chinami does, and then lets something slip).
As far as who we won't get, the only girls I can see not getting anything, and this totally depends on if it is outside the comfort zone of the developer in most cases, is Chinami and Tsukasa, both for reasons that it would result in content that is becoming increasingly banned across the internet. We're talking about the same kind of thing that Patreon struck Selebus for here, at least one of the reasons they struck him.
Of course, this is only a guess based on the lack of content for those types of characters in the game and I could be completely wrong, meaning we could eventually get some, it just would not be mentioned anywhere that bans that content and may not be acceptable to be directly linked here depending on what the mods think as far as how these characters fit into rule 7. Remember that F95 rule 7 is not a total ban on that type of content, just a guideline as to what may or may not be accepted, and that the mods and admins have the actual final say on a case by case basis.
Every character has been stated they will get some sort of content, both side and main.
How do I see the roommate and other relationships going?
I don't see Yumi/Chika ending badly unless Yumi gives in to her dislike of Sensei and tries to tear Chika away from him without any valid reason like actual evidence of cheating or something.
Ami/Ayane I actually don't see ending badly on Ayane's end, BUT I DO see it ending terribly on Ami's end. Given her
instability and
possessiveness, I could see anything from a major friendship ending fight to actual cold-blooded murder to keep Ayane away from Sensei considering she is one of my yandere candidates at this time.
Rin/Futaba is where things get dicey without a doubt. We've already seen how Rin
reacted to Molly, she is nowhere near in the right mindset to think calmly and logically about things like this. Futaba could and likely will get hurt by Rin due to her
complete romantic tunnel vision that leaves no room to care about anyone else.
Karin/Kirin I see the potential for a sibling fight and probably Karin thinking she was betrayed by both her own sister and Sensei, but nothing too major, at least not compared to Ami/Ayane or Rin/Futaba. There is a possibility of Karin heading down a very dark, potentially suicidal path, but the possibility is tiny compared to Rin as I see it now. At least, this is what I think if Karin catches Sensei with Kirin, things get REALLY dark if Kirin opens her big mouth about the things she knows of Sensei being with other girls. That could not only be completely devastating to Karin, but to any other girl she tells, and HOPE forbid she tells Yumi that Sensei is
cheating on Chika behind her back, there would be nowhere to run or hide, that girl would turn the entire town on its head looking for the cheater who betrayed Chika. That is one hell of a scary thought and it hasn't even happened. Yes, I am legitimately scared of the prospect of Yumi angry because of something Sensei did to Chika, that girl terrifies me at times with how protective of Chika and Chinami she can be, but at the same time it is both noble and kind of cute.
I don't see a move on Yumi even happening, she knows
Sensei is with Chika and betraying the one person who she is closest to is the last thing she would do. Before we ever get to Yumi, I do see something happening between Sensei and Chika to end things, at least as far as
actually dating, I don't know if she would also stop letting him do things with her.
The only Main girl that's optional is Ami. As in, not only is it possible -- you will HAVE to when the time comes. Selebus was quite clear on that. Unless he's changed his mind, that also means that Bad Homie players are still likely to wind up shagging Rin at some point. Though it might be a hatefuck.
As for the side girls, I suspect all of them will be bangable before its over. Even the lesbian karate instructor. They won't be automatic, and it might be very easy to miss your opportunity with some of them, but the option will be in there, somewhere.
Selebus has made no sign that his mind has changed about who will get any kind of content since the beginning, either here or on any official channels, and he was pretty explicit that if a character is presented in the game, they will get content. Things might get questionable as to whether Chinami or Tsukasa might get involved because of how things are progressing on the internet as a whole as far as their type of content, but anyone else is, so far, going to get content. I definitely could see a Rin hatefuck, that seems like the best way for things to play out for bad homies unless the plan really is to lock out bad homies completely from anything sexual with Rin. I can still definitely see a complete lock out, Selebus does like to implement actual meaningful consequences like that.