No body can bury the Shield. People have been talking about how they want to push Reigns since FCW. Reigns is the next big thing that WWE wants to push to the moon.
Cena didn't keep his spot this long by being dumb. Doing the usual and turning Bryan heel to feed to him would have gotten him heat. WWE fired Bryan and the fans got him rehired. The 15 second squash match killed Sheamus's push. Cena uses him in the other way he uses guys; he uses Bryan to get face reactions. Similar to what Hogan did with popular guys. For a while there Bryan nothing but a "Cena buddy," where Cena did all the talking an fighting for him against the big bad authority, making Bryan look weak in the process. And we all know Cena will go over Wyatt for his "pal" Bryan.
That was just to drum up interest in the match to sell tickets and PPV's.
No they didn't. Vince personally told Bryan they were going to "release" him for a little while to appease sponsors. They told him he'd be back once it blew over. He was the last surprise entry to their SummerSlam team. Again, look at Bryan's career in the WWE so far: NXT with the Miz, comes in with Nexus, gets "fired," returns at SummerSlam as a face, goes on to win US championship, loses it, goes on to win MITB, cashes it in to become WHC, loses it, goes on to become tag team champions with Kane, loses them, and fast forward to here. That's a pretty natural progression for 4 years/somebody who seems to be constantly on their way up in the company..
Anyway, can't bury people you've been booked to lose against. Plus it's lose-lose for Cena, you try and put people over in a segment that doesn't involve them and people will hate him for "leeching." Did he need to mention Ziggler in the unified championship promo? Probably not, but ya know, he's looking to steal Zig's reaction