Ok here are some of my thoughts and theories. First of all, I think its safe to assume that the winner will be a Smackdown guy. Reason being that Raw has the Chamber PPV, and since Brock wont be defending the title that night, the chamber match will be a number one contenders match for the Universal title. This way Roman gets his first Chamber victory, and he goes on to main event Wrestlemania against Brock, so its actually quite a nice setup. Now, as far as the Rumble match winner, I have 4 people in mind.
1. Nakamura : It is no secret that Nakamura vs Styles is a dream match that everyone wants to see. I mean just look at the reaction they got in the MiTB match, the crowd went nuts (and that was just a stare down). Now imagine giving them a world title match on Wrestlemaina, it would go down in history as one of Wrestlemanias most memorable and greatest matches ever, without a shadow of a doubt. This, in my opinion is the most logical and safest decision they can go with, I mean as far as Wrestlemania dream matches go, it doesn't get any bigger then this one. The biggest problem here is Vince,and if he is willing to give a Rumble match victory to a guy like Nakamura. Hopefully he will see the massive potential that this match has, and give the green light to Nakamura.
2. Either Kevin Owens or Sami Zayn :The idea here would be to have 1 of them win the rumble and the other being the champion going into Wrestlemania. So who would win the Rumble? Well the same thing I said about Nakamura winning applies to Sami, in fact even more so. I just don't see Vince letting a guy like Sami win the Rumble match. On the other hand, I can definitely see Owens winning, even though I would prefer it, story line wise if Sami won the Rumble, and Owens beat Styles for the title. So Owens wins the rumble while Sami is the next challenger for AJ Styles, at Fastlane. Owens promises Sami to help him win, which he does, screwing AJ out of the title, and setting up a match between the two best friends at Wrestlemania for the WWE title. Now just as Owens and Zayn think they got the match that they always dreamed about, out comes Shane to screw it all up, adding AJ to the match and making it a triple threat. This a perfect way for Shane to finally get payback at the two, messing up their Wrestlemaina dream match. It also makes sense to add Styles to the match, since he was screwed out of the title. In the end, Owens wins the title screwing Sami in the match yet again, setting up a feud between the two for the months to come. This is how I see WWE doing it. I would do it a little bit different, like i said having Sami win the rumble, and Owens the title. Everything else would remain the same, Owens screws Zayn in the match retaining the title. Then a baby face Sami Zayn starts building momentum in the following months, all leading to a one on one match against Owens at Summerslam, where he finally wins the WWE Championship.
3. John Cena :Simply because I don't see him doing anything else at Wrestlamania. And yes while another Cena Styles match would be cool, there are a lot of better options. Also I really don't want to see Cena winning the rumble, especially because Orton won it last year, and Triple H the year before. Its time for someone younger (that isn't Roman Reigns) to win it.