Apple's attempting to set a new expectation with consumers: OS updates should be free. Users are already accustomed to it on their phones, now they'll start to expect it of their computers.

I'm willing to wager that Apple never charges for an OS update again. I'm surprised they've taken this long to make the leap. (Of course, Microsoft makes more from OEM licensing than upgrades, but it's still a blow to their value in the consumer headspace.)