Long time fan that's going to break down the situation. I see lots of guy's on here saying "AJ Styles is the best, KEEP HIM A FACE AND TURN REIGNS AND CENA HEEL!" This isn't going to happen lol. Essentially the WWE is using NXT, as well as Japan leagues as bad guy factories to churn out competitors for Reigns and Cena. So any time some new guy comes up and feuds with either dude, you should be expecting them to ultimately lose.
Cena should be putting people over right now, as he's pushing 40 and has been the top face for 11 years, and Reigns isn't main event material, which I'll get into below. Feeding the Japan wrestlers and NXT prospects to Cena and Reigns is backwards booking.
Why don't they just put the belt on a guy like Rollins or Styles instead? Because the guy's lack casual appeal. It will sound crazy but many people are interested in wrestling to see two giant power houses facing each other, and the idea of a guy like Styles, who isn't exactly the most imposing presence, isn't going to bring eye balls. Now when I say "eye balls", don't get me wrong a lot of people cheer for him and I personally like the guy a lot, but the type of fans he has are likely going to watch the product anyway. That's how it has always been, and that's why the WWE will toss the "hard core marks" a bone here and there, to keep them hooked, but overall, they are trying to get other types of fans watching the show as well.
Heidenreich, Snitsky, Nathan Jones, Tomko, Khali, Mason Ryan, Big Daddy V, A-Train, Test, Luther Reigns, Kenzo, etc. are all examples of why just being big is NOT enough to appeal to casuals, as they ALL lacked charisma, mic skills, and in-ring ability (I know A-Train became Giant Bernard but before that). Reigns fits into this category as he lacks everything but the look. AJ has charisma and in-ring ability, which gives him more of the criteria than any of these big guys had. The big guys that became a big success, like Lesnar (great in-ring ability along with the look), Goldberg (the look and VERY charismatic), Batista (ditto Goldberg), Warrior (ditto Goldberg and Batista), Cena (great look, mic skills, charisma, and in-ring ability), Undertaker (solid mic skills, very charismatic, great in-ring ability, and the look), and Hogan (great look, extremely charismatic, and great on the mic), all had at least two out of four (charisma, mic skills, look, and in-ring ability).
Now you may say, "Well Roman doesn't have many casual fans!" that may appear to be the case, ratings have still gone down from what I can see with Reigns as the champ but the WWE network has been steadily increasing subscribers, which would indicate that while Reigns is hated by hardcore marks, most people don't mind him having the belt and are still giving the WWE their money.
The WWE Network now features Raw replays from 1993-2005 (New Generation, Attitude, and Ruthless Aggression eras), Smackdown replays until WM 20, all Nitros until mid August 1999, and all ECW episodes, along with every PPV from WWE, WCW, and ECW. Most of that wasn't on the WWE Network a year ago. Nostalgia sells, so I don't consider that having anything to do with Reigns.
I know some will say, "They would be making A LOT more money if they put the belt on a guy like AJ Styles" all one has to do is see how hard TNA has flopped though to show that AJ while popular with people already watching the show, has not had any sort of track record of bringing in new fans (at least not a good one). Ditto goes for the ROH style in general, we see tons of people wanting the show to pretty much just push guy's that were in ROH (and then NXT), yet the reality remains, ROH has never been popular. Many wrestling fans have not even heard of it, not only that, but the ones that have may have never seen one of their shows. If the ROH style was as great and popular as some on here describe - by this point the ROH would be a serious competitor with the WWE. The exact opposite is the truth though.
AJ has nothing to do with TNA being in the position it's in... TNA's booking has been the biggest reason, along with trying to be better than WWE rather than different, relying on older talent to carry the company, and constantly changing their direction.
Theoretically speaking though, let's assume these ROH guy's would bring in a lot of money. It would still be a bad idea to use them because their ring style is not smart when working as main eventers. Daniel Bryan and Seth Rollins are too good examples of this. As a main eventer, you want to work a safe style where you don't take too many unnecessary risks, as an injury can screw everything up. With Rollins and Bryan though, we saw they did nothing like this and in the process the product suffered. When you've been in the ring as long as these dudes have, you should be able to work a relatively safe match that can still get the crowd going crazy, it appears these guys have not learned that part of wrestling though yet.
Some of the most injury prone wrestlers are those who work "safe styles"... Edge, Orton, Batista, etc. And when the X Division was in its prime, the wrestlers hardly ever got hurt. Jericho wrestled more of a high flying style and I can't remember him ever getting injured. Wear and tear, which a schedule like WWE's can easily cause, is a bigger factor for injuries than the style somebody works. I'd feel much safer working with somebody like AJ than somebody like Khali or Ryback...
Anyways, don't hate the messenger, I'm merely explaining why the WWE does not push some of the smaller flippy guys to the top spot, since this type of stuff is posted non-stop every day on the site. These guys will still get pushes, it's just not going to be to the level many of you guys here want. So in short, there's no reason to expect AJ Styles or some of the other guys (Rollins, Kevin Owens, Sami Zayn) to get pushed above guy's like Cena or Reigns. Cena or Reigns are not going to turn heel and be fed to these guy's because the WWE would likely lose a lot of money. The NXT and NJPW guy's are ultimately enhancement talent, used to keep the top guys looking good and keep them feuding with fresh faces. As long as you keep expecting them to get wacky pushes though, you will ultimately end up getting angry pretty much every Monday Night, as well as on one Sunday a month. The only thing you can feasibly do is stop watching and watch other wrestling shows instead.
Which is backwards booking as Cena doesn't need rubs anymore, because he's JOHN CENA and already has a HOF spot locked up, and Reigns as a main eventer/top face just isn't working. People like Rollins, Owens, Zayn, Rusev, and Ambrose (who SHOULD be the top face right now) SHOULD be getting wins over the likes of Cena these days... I'm not saying that Cena should be losing to people like Heath Slater, but it is clearly time for him to be giving rubs to the younger wrestlers as he's 39 years old and isn't getting any younger. A 40 year old as one of the top faces, if not THE top face, reminds me a lot of late WCW, which today's WWE has a lot of similarities to.