I do wonder how they'd build up Taker/Cena with promos and stuff. I hope they do something interesting, specifically Taker. Cena's obviously gonna be saying stuff like "I respect you, and at Wrestlemania I intend to end the streak..." blahblahblah. Honestly I'm worried the build will be a lot like Taker/HHH WM27, which was incredibly bland and nearly put me off from anticipating the match (would've if the last promo between them with HBK didn't deliver).
They should play in Cena's loss to Rock last year, and how after that he needs to end the streak to regain everything he lost that night and to be able to cement himself as the number 1 superstar of all time (especially since during his arena promo, he brought up how he doesn't want to be number 2). Of course the loss to Rock will still loom over him even if he still managed to end the streak, but the fact is he would've ended the streak and kayfabe wise he could be regarded as the greatest of all time for that in addition to his other accomplishments.
However, I would go with him losing the match to Taker, which forces him into depression and making him come to the realization he just can't win the big matches anymore (kind of like what they did with Jericho/Ziggler, only Cena has won more than just one big match). He goes on a losing streak (use this to put over a rising heel huge like Sandow, Rhodes. Barrett, etc.), and at MITB or after, he wins a number 1 contender's match to face the WWE Champ at Summerslam (who we'll assume will be Ryback). The win will be the first in months but it'll come either due to outside interference as someone costs Cena's opponent the match, and Cena willfully covers them for the 1-2-3 (we'll say the person Cena beats is Sheamus), however he doesn't know who knocked out Sheamus... or so he makes it seem. The slow heel turn starts. For weeks leading up to Summerslam, he'll do little things in matches to win them against low card heels/faces. Maybe eye pokes/eye rakes at first just to win matches going into Summerslam. He faces Ryback in a match that's relatively clean, and in the end of the match after a second AA(and maybe third AA if they want to go crazy), Ryback kicks out and Cena flipping out on the ref... briefly, but he does it. He then aggressively locks the STF on Ryback, and Ryback makes it to the ropes. Cena however, unlike the usual face routine, doesn't let go and waits for the ref to count to 4 before letting go. He makes a move to seemingly hit the ref, but stops his fist and regains his composure. He goes to pick Ryback up but Ryback maneuvers him into shell-shocked and wins the match.
Cena gets a rematch against Ryback at NOC. Leading up to NOC he starts using more heelish stuff during and even after his matches. One week he makes someone tap out but doesn't let go of the STF until the ref and anyone assisting the ref forcefully pulls him off. Another week against a top level star he pulls the tights to win the match. All throughout Cena in his promos is making hints that he's been getting annoyed with the audience and people accusing him of cheating, but he doesn't say anything drastic. He goes on to NOC, where Cena uses tactics such as feet on ropes during the pin, not letting go of the STF again when Ryback gets to the ropes and he targets a leg of Ryback throughout the match. Ryback through it all stays alive, and Cena gets Ryback on the top rope and hits an AA off the top rope, and Ryback kicks out. Cena explodes in anger at this point and in blind fury gets out of the ring, grabs a chair, and starts hitting Ryback with the chair over and over again. He just beats Ryback with the chair until refs and security manage to hold him down. The PPV ends like that.
So Cena is now on the heel side of tweener, but he's still not a full-blown heel as he apologies to Ryback and to the fans for his unprofessional conduct, and that he's never lost control like that before. In a triple threat, similar to how Punk won the match at Summerslam this year, Cena wins a number 1 contender's match (for hell in a cell) in the same way. Ryback comes out and the two brawl but Cena gets the upperhand after kicking the leg he worked on in the match at NOC. Ryback seems to be about to get the momentum back on his side before security breaks them up and gets Cena out of the ring. The next week Cena doesn't appear on Raw and makes it seem as just having a day off. Of course beneath the surface, Cena is starting to slowly want nothing to do with Ryback, because after how Cena destroyed Ryback's leg at NOC and beat him down, Ryback still came back for more, which is something Cena wasn't used to. Cena then does stuff like having his music played to distract Ryback during matches, delivering an AA to Ryback following a match followed by trying to rip the knee Ryback has injured (due to Cena) and then the following week saying it was just him making a statement, but still to keep people wondering if he was a good guy or bad guy, apologizing for what he did and stating that's not the code he lives by, and all that. HIAC rolls around and Ryback still has the injured knee, which Cena takes full advantage of throughout the match. Cena uses ring steps, chairs, keno-sticks, and the cell a bit to destroy Ryback's injured leg, his vertical base, and any hope of him hitting shell-shocked. Cena hits an AA, but doesn't cover. Instead he pounds on Ryback's leg and his body with a chair similar to how Stone Cold was pounding on Rock at WM17. He drives the chair into Ryback's injured leg multiple times before stopping and covering Ryback. Ryback kicks out, so Cena wraps the chair around Ryback's leg, goes to the second rope, and comes down on the edge of the chair, closing it in on Ryback's leg (think what Snitsky did to Kane at Taboo Tuesday 05 since I'm bad with descriptions
). Cena pins Ryback again, and Ryback somehow musters up the strength to kick out. Cena at this point is losing his mind and is having trouble coming to grips with having an opponent he just can't put down. So he picks Ryback up and hits the AA. But he isn't sure if it's enough, so he places a chair in the middle of ring, hoists Ryback up again and hits a third AA, but this time on the chair. He goes for the cover and the ref makes the 1-2-3. Cena's the new champion, but at this point he knocks out the ref as the ref raises his hand. He then demands the cell be lowered, and proceeds to continue working out Ryback's leg with the chair, steps, and whatever else you can imagine. Finally he stops, holds up the title, and for the first time in two years he is the WWE Champion, and now he's a full-blown heel, and makes a promo the following night.
Okay, I'm getting tired of typing, and I typed most of the stuff I was interested in getting out anyway. So to conclude, at SVS he and Ryback lead teams against eachother, which Ryback comes out on top of. Cena beats Ryback at TLC to retain the title, and Ryback doesn't get a rematch at RR. RR comes and Cena costs Ryback the Rumble. Ryback however wins an EC match to become Number 1 contender for the WWE Title. He goes to Wrestlemania and beats Cena for the title. They continue the feud with Ryback coming out on top. Cena then goes to Smackdown and becomes the dominant heel WHC for most of the year before putting over another face hugely at WM31 to cement them as a main event stay. I understand Cena on SD might seem a bit out of place, but from where I sit it would add freshness to Cena and bring ratings to the SD brand which it so desperately needs.
Although my idea comes with the thinking Taker/Rock would happen at WM30, so Rock would be occupied. Another road is Cena moves past Ryback and Rock wins the Rumble to challenge Cena. Then they can either end Mania by sending the fans home happy with Rock getting his 10th title win, or having Cena absolutely destroy The Rock, putting him over even more so as the heel WWE Champion. Then Ryback could take the title off him at SS, or if they want to stretch it, have what I said in the above paragraph from RR-on happen but just a year in the future.
Oh wait, this thread is about Taker's streak match. Damn, got carried away there. Maybe Cena faces Taker in a rematch at WM30 as a heel and ends the streak. Meh, I'm exhausted.