The parallels with Windows and the Mac don't stand up.
Standards, largely around the internet, mean that there is no real drive for there to be a single winner the way there was on the desktop at that time.
I have an iPhone, you have an Android phone and we can both text each other, mail each other, tweet each other, share photos, contact each other via Facebook, share links and documents, IM and the rest.
That wasn't true back in the days of Windows vs. the Mac and that was why Windows won out - if you were in the minority camp back then you were genuinely being excluded.
But now users can work together regardless of platform, Apple make money, Samsung make money, Google make money. There really is no drive towards a single platform. Sure those companies all want market share but there's no reason to believe that it has to end up with a single dominant MS-style player.
And in terms of market share numbers it's not clearly trending in that direction. Until very recently both iOS and Android were gaining market share (squeezing Windows Mobile and BlackBerry). Google has a larger market share yes but it's not winning at the expense of Apple, they're both winning at the expense of others and grabbing more of the first time smartphone customers.
As regards the most recent market share figures [1], if anything the momentum is moving away from Android. Android market share actually dropped while iOS continues to grow.
It's still around 50% and I don't think anyone is suggesting it's in any sort of trouble (Horace's headline is a little mischievous), but the narrative that you're suggesting isn't really supported by what's happening.
What really looks like it's happening is a market dominated by two players with everyone else fighting for scraps.
[1] http://www.asymco.com/2012/06/04/trouble-with-the-robot/