Who is alive at this point?  Does Walt have cancer?  Why did he drive back across the country after being gone for some period of time?  What could possibly have happened that makes him want to kill?  That to me, is the biggest question
		
		
	 
It's all a misdirection. In the Denny's, where Jim Beaver, the gun dealer meets him and exchanges cars, Walt picks up the M60 machine gun. If Walt was outed as Heisenberg, and that's public, there is no way he's out in public eating in a restaurant and there is no way a gun dealer, no matter how much they like money, would want to risk dealing with someone so high profile and public at that point. The Jim Beaver character, despite a couple of short scenes, is shown as pragmatic and logical and very discrete. There's no chance he'd give Walt the M60 if Walt was "on the run" and have that weapon possibly traced back to him somehow.
The Carol neighbor is another misdirection. She's not in shock because Walt is known publicly as Heisenberg, she's shocked because it's assumed Walt is dead.
"Heisenberg" in that house could be a common tag or graffitti at that point in the show.
There is only one true "endgame" from a writers standpoint. Everything Walt has been involved in, Hank has been involved in, but mostly without Hank's knowledge.
Hank has a bald head/shaved head like Heisenberg.
Hank has all the information through his job to meet connections in the drug world.
Hank has all the experience with drugs to be a credible ring leader of a massive drug operation
Hank has been at the center of a lot "violence" regarding the blue meth. He shot Tuco to death. He killed the twins in the parking lot. He was the one who persisted on Gus Fring, and he was the last person to see Fring before he blew up in a nursing home. As a drug lord, Hank has motive to kill all his rivals, including all the cartel members.
Hank "survived" the turtle/Danny Trejo head bombing, which killed a ton of law enforcement agents. What a coincidence.
Hank "knew" which evidence holding area had the laptop, and had it destroyed.
Hank would have the connections and means through law enforcement to conduct a multi stage hit across several facilities all at once.
Hank has many expensive rehab and medical bills paid for, but it's not commensurate with his actual income. His only contention is that his brother in law and sister in law, one with cancer, the other only a part time book keeper, were able to keep him afloat with gambling money.
Hank beat Jesse Pinkman, someone at the center of all of this mess. Miraculously Pinkman recants wanting to press charges. Miraculously as Hank looks to lose his badge, he's a hero for killing the twins.
Hank "forces" Walt and Skylar to run the carwash to launder money, to distance himself from it, threatening them to do it. Hank "takes in" Walt's kids as leverage and to threaten him.
Walt's ONLY play is saddle the Heisenberg personality and activity onto Hank. 
Walt and his family are passed off as dead for their own protection and put into government WitSec, given new identities and a new location, to protect them from "Hank"
Hank is the only truly moral and redeeming character in the entire show. He was willing to take in Walt's kids. He was willing to take responsibility for Skylar and the children financially if Walt died. Even when he beat Pinkman, he was remorseful and acknowledged maybe he should lose his job. He has tried to guide and be a positive influence on "Flynn" The worst thing you could say about him is his treatment of his wife after he was shot.
In order for Walt to "break bad" and never come back from it, he has to burn down the only truly good man he knows. And he can always say that any involvement on his part was by being tricked by Hank or coerced by Hank or enticed by Hank to say that the exchange would be to take care of Walts family after he died. That Hank forced Walt to put a former student, Pinkman, on his radar to be used.
What is more plausible to the press and law enforcement? A veteran DEA supervisor "breaks bad" and becomes a powerful underground drug lord or that a mild mannered Chemistry teacher, a dying one with a crippled son and a newborn, with a wife with limited job prospects with no connections and no criminal history would be one of the most powerful people in the entire drug trade across the world?
The show is going to end where it began, with Walt dying and leaving his family behind saddled in debt and with no future and limited prospects in front of them.