Cena wins the unified title. Heyman returns and Lesnar vs Cena is booked for Royal Rumble. Lesnar beats Cena with Heyman's help. Punk wins the Royal Rumble. Cena wants his rematch to be inside Elimination Chamber. Lesnar vs Cena vs Orton vs Bryan vs Sheamus vs HHH for the title. Lesnar retains and the Heyman-Punk payoff is for the Undisputed title at Wrestlemania.
Wyatt Family and The Shield clash in the Royal Rumble match and have the first ever 6-man tag match inside the Chamber. Wyatt Family takes the win. Hulk Hogan is announced as Wrestlemania host the next night. The Shield surround the ring and Cena tries to make the save. After months of teasing a return Taker comes out and fights off The Shield for revenge. Then Taker and Cena stare down and look up at the WM logo with Hogan standing in the middle to end RAW.
Either Cena vs Taker happens at Wrestlemania, OR it was a tease for WM 31 and Cena instead teams with Hogan (and The Rock if he returns) to take on The Shield. If the latter happens, the Wyatt Family would target The Undertaker, abducting Kane. They would bring him out tied to an Undertaker-style cross and pour (fake) gasoline over him. Bray lights a match and talks about the fire being Kane's beginning and end. Lights go out and Taker appears, but is beaten down by the Family. A Buried Alive match is announced for Wrestlemania.
HHH placed himself in the Royal Rumble at 30, but was eliminated by Bryan. He then inserted himself in the EC match and conveniently was released last from his chamber. During the EC match for the title HHH is eliminated by Bryan and then causes him to be eliminated after. This sets up a grudge match finally at Wrestlemania. Bryan could represent either Vince or a returning Shane and the match could be for control of the company as well after HHH started abusing his power even more.
Goldust costs his team the titles and gets paranoid that everyone thinks Cody is the better brother. He snaps and it leads to a Wrestlemania match, possibly with Dusty as the referee, or just at ringside. Retirement could be on the line for Goldust if he thinks ending his career with his dream Brother vs Brother match is worth it.
After beating every diva in the company AJ cuts a promo about not having any challenges. This could lead to a return of some kind. Trish would be great, Kharma would be awesome too. The best option would be Lita if she were willing to come back, with AJ's idolization of her being central to the storyline and maybe resulting in an AJ face turn at Wrestlemania.
The Cruiserweight division is reintroduced and a tournament for the vacant title is set up with the likes of Mysterio, Sin Cara, Kidd, Gabriel, Woods, etc. Mysterio and Sin Cara meet in the finals in the Wrestlemania show opener and WWE tries to break that most masks worn world record thing with the crowd.
Brock Lesnar(c) w/Paul Heyman vs CM Punk(RR) - Undisputed title
John Cena & Hulk Hogan (& The Rock?) vs The Shield
Bray Wyatt vs The Undertaker - Buried Alive Match
Daniel Bryan w/Vince or Shane vs HHH w/Stephanie - Control of the WWE
Cody Rhodes vs Goldust - Retirement Match w/ Dusty Rhodes as Referee
AJ Lee(c) vs Lita - Divas title
Rey Mysterio vs Sin Cara - Vacant Cruiserweight title
Cena vs Taker and Wyatt Family vs The Shield (losing team disbands) could be an alternative as well. I just think it'd be a shame for Taker to retire without feuding with Bray Wyatt. The build up would be epic.
Big E Langston vs Mark Henry for the IC title is another possible undercard match. Neither has to turn heel, Henry can just win a #1 contender battle royal and a staredown between the two is enough to sell this one.
With the tag team division looking as good as it has I would like to see either a multiple team ladder match or a Tag Team Turmoil match as well. Cesaro and Swagger would win the titles off of The Rhodes Dynasty and be champions coming in. I think with the tremendous work they've put in it is a shame that the Usos have never been champions, so it would be great for them to win their first titles on the big stage.
Big Show, Del Rio, Orton, Ziggler, Sheamus, Jericho, etc. could possibly compete in a number one contender battle royal of some sort. I think bringing back Money in the Bank would be a great option too, since it started at Wrestlemania. I'd love to see Ziggler win the match early in the show and then come out to challenge Punk at the end, saying he has dreamed of main eventing WM just like Punk and he isn't waiting another year. If anyone can give two great matches back to back at Mania it is Punk. That could be overkill though.