Now, there are a lot of reasons to believe it: It's the summer of '69, and Megan's an actress living in the Hollywood Hills. Don has made numerous references to her being alone there and how the coyotes' howls echo eerily through the canyon. But, coyotes are prone to howling and Don is prone to controlling, so everything is as it should be. Yet, there has always been an air of sadness shrouding Megan despite her being such a magnetic character — the show's lonely optimist — and it's hard not interpret that as some kind of sinister foreshadowing.
We could go back through all the plot points that hint at Megan's alleged demise. She wore the same T-shirt that Sharon Tate wore in a magazine, and Peggy held a can of Folgers (one of the Manson Family's victims was Abigail Folger), but most can be explained by the fact that this show is set in the same time period. Folgers was the Starbucks of the '60s and knowing the show's obsession for period details, maybe that star tee was everything to a young actress who read magazines.
While there is something to the idea that Matt Weiner is messing with us — these rumors have been flying around since before this season was even filmed — the biggest reason Megan will not be murdered is that this is not that kind of show.
Mad Men has always delighted in the quiet drama of our existence. Yes, crazy things happen (the lawn mower incident, the bayonet stabbing, the severed nipple), but they happen in doses that are measured enough to be believed. The show itself is about times that are changing and a man who refuses to. How far does he have to be pushed, how much does he have to lose, and what happens if he simply can't? That's what Mad Men has been about since day one, so for it to suddenly place itself in the middle of one of the century's most infamous crimes would completely derail the show from its very calculated path.
Besides, it's summer. It's 1969. Isn't there a moon landing and a very well-attended concert to mention?