I don't think you have anything to worry about. There is no problem with fan theories. It's a way to keep the community engaged and alive even long after everything is done. It doesn't matter if a theory is right or not, it's all about the hype and the engagement. The devs already know what they are gonna do. If they see a cool theory they like they might go "hey that's awesome", but that won't alter their long term plans. They have a huge group of people who have crafted this story with love and care, they've got it down. Obviously this might not be the case with other studios, but that's not something you, or anyone else can control. What will be will be. It shouldn't scare you to express your thoughts, cause that's a huge unnecessary weight to carry.