Right now, the only obstacle to Amazon's profitability is Walmart. If Walmart didn't exist, Amazon's pricing control supremacy would ensure they could operate at the lowest possible market price on every item, and as the market maker for product, they would control the cost floor as well.
In a sense, the end game for Amazon is this: it's fucking ludicrous to run a company without profit for years. At some point someone else is going to try to take more profits because of the volume pressure of Amazon. The end game for Amazon is choking all of the other retailers out of existence, IMHO.
They don't have to flip a switch, they just need to wait. They're playing the long game.