And what about Tiffany getting pregnant with the MC's child (after her wedding?) It would be nice if that's a thing or dating her.
Also, for your first reply, I love spoilers so I can look forward to it since hearing vs experiencing are 2 different things to me.
Alrighty, you asked so I'm going to give you my thoughts on letting Bailey go. Just know you unleashed this evil on the thread.
So let's go back to what was happening to Bailey and where she said she was going. In that scene she was losing her mind and going back to a portal to the black sea. This black sea was unknown back then but now we've visited it in a dead end when trying to kill Charlie. In that scene, MC met several different monsters that terrified him. Monster that were far above Level 3 in power and by the end, he fell prey to one in the black waters. That's where Bailey is going.
Now let's look at Bailey and what she is. She's a partial Minyak/zombie. Her primary function is to be bred and eat women to help make that easier. We can see this in her desire to have MC's children at every meeting. Her max class is D but she's likely lower. In case you don't remember the ranking system, D Class is 2nd to last in power. She's pretty much weak and can't increase her power any higher. Even if she could, at most she would reach C Class, which is only Level 2 in power. Any monster with more offensive abilities can kill her or breed her....
So, Bailey, who has given in to her instincts, which are that of a Minyak, is going to a realm full of monsters that are much more powerful than her. When she gets there, the natural conclusion is she'll be bred by stronger monsters and maybe birth a couple of Minyaks. That's if she isn't killed by anything else that comes across her. Basically, letting her go is going to result in Bailey becoming one oily ass pocket pussy for the monsters out there. That's if she survived the journey of course.
Now back to your first question. The answer would be no. Maybe Tiffany marries MC at the end but she just got her freedom back. I doubt she'll give it up again. She's also not pregnant because Superhumans can't breed with humans or each other, currently.
The only things Superhumans can have children with is monsters and only a select few of them. The known ones being Aglaecwif, Eisheth, Gorgon, Sewer Monster, Minyaks and Rebis Deryl. We got confirmation this update that Ella can be used for breeding though we don't know if the 4th was referring to her monster form or Superhuman. That should give you a general idea though.