OK, things are getting interesting. I don't think anyone needs to worry about Fortnite. It's popular now, but it's staying power has yet to have been tested. Putting them in right after Minecraft would be jarring to say the least since Minecraft firmly established it's self to be a juggernaut that will be around and relevant for a long time while the Fortnite popularity may fizzle out within a few years.
Not only is it's staying power in question, but at the time that characters were being selected it wasn't even at it's height of popularity, so it wouldn't have as much clout then as it might now.
Doom Guy could happen, but I still personally don't see him working well in smash. While other violent characters have gotten in like Snake and Bayo, neither of them are so know for just how gorily they take out their enemies.
Hayabusa could happen, but I wouldn't put his odds any higher or lower than anyone else.
I wasn't the biggest supporter of Crash's odds, but right now he does seem more likely than most. That "woah" tweet in particular. Everyone involved knows how fans scrutinize every little bit of info, so Geoff posting that was either a hint or an intentional misdirection.
Also Crash has a few things going for him that others don't. In recent years, Coco has been boosted up to basically be his player two, being able to do anything he can. This means she could easily share his spot as half the costumes. If this is the case then it could account for that extra space for fighters voices that was found a while ago.
And as others have said, if Crash gets in that doesn't mean the leak that mentioned him and Shantae is legit, but it does keep that leak alive a little longer.
fortunately we won't have to wait long to find out.