I have a new favorite theory.
1x12 "Faith" introduced us to the idea of reapers under the employ of another; and 4x15 "Death Takes a Holiday," how many shits Death cares about that. In 8x19 "Taxi Driver," we learned, among other things, that a certain faction of reapers have stepped out of their traditional roles and are moonlighting as Purgatory's boatmen.
We also learned that, evidently, Crowley's not paying a whole lot of attention to Hell, since now that Purgatory's has been located, period, someone's gone and poked a hole through from Hell; and of course, we learned in 8x23 that Heaven is empty and all the angels are here.
I know that everyone and their pygmy goat was annoyed with 8x19's deceptively easy, bootleg way of transgressing cosmic boundaries, given how difficult it used to be to get someone out of Hell, find Purgatory, etc. Not my favorite, either! But nine years ago, it was really difficult for a demon to find its way topside, and angels didn't even exist. Times change, and the world's been flirting with the entropic for a long time coming. And on this basis, SPN has built a stairway to a very specific nowhere.
IN 9x03, SHOW FINALLY MAKES IT TO DETROIT. 9x03, brought to you by the same folks who gave us 8x19, returns us to the idea of rogue reapers, and also to the idea of Death not giving a good goddamn, as he is conspicuously absent of and silent on this phenomenon.
He made his brief appearance in 9x01, but only to impress upon us that Sam's choice to live or die was in his hands (which, if we were paying mind to the natural order, which Death thought it prudent to remind Dean of in 6x11 "Appointment in Samarra," it certainly would not be). But with Hell the way Hell is, and Heaven the way Heaven is, and the angels and reapers and demons claiming open season, order's lost the high ground.
Instead, we have chaos. Or Chaos, the unformed matter through which Lucifer Fell (according to Milton, according to Hesiod), the universe outside of God's purview--that is, Death's kingdom.
What I mean is, in 5x21 Dean shares a pizza with Death, and Death shares with Dean the end of the universe: In the end, he will reap God, too. When the world tips from God's creation and into Chaos, into Death's backyard, then he will be there to reap God, too.
You needn't flush God out with any amulets if his kingdom simply slips into yours. Because in the end, Death knows, we will always end up here.
BADUM. BOOM. CYMBALS.
But hey, that may actually be more likely than you think, because so far S9 is basically just one long love letter from SPN to me. Which is refreshing! Because while I like S8 well enough, IT DEFINITELY HATED ME. XD
Special thanks to counteragent's 9x03 reaction poll, without which I never would have stumbled upon this train of thought.