Antitrust on their high prices maybe, a Monopoly on products I don't think so; there is enough competition.
For now there are a lot of competitors. But ALL of the competitors in the high price smartphone area seem to have lost a lot of money on their phones last year, except for Samsung.
What happens next year? I assume HTC, Nokia, Motorola, BBRY, LG, etc. make another flagship phone because what else are they going to do? But what if that also loses money? What happens the year after that? How many of these guys are around making a flagship phone two years from now? What if Apple's next phone is really a big improvement? What if they innovate again and in a big way? it wouldn't really take all that much more to make the rest of these folks have to pack up shop would it? They must be hanging by a thread right now. Can any of them drop a billion dollars next year on R&D? Apple can drop $5 billion on its phone without batting an eye. (Yes, I know they've never spent that much, but they could. The others, except Samsung, can't.)
Ad buyers are discovering that advertising on Android phones is much less valuable than iOS. That ad money is going to drop away. Advertisers will push the price of those ads down if they don't start seeing more results. With ad money dropping away, then developers are going to decrease developing for android phones. Already many big players (see Nike Run App for their fuel band) don't make an Android version. This might get worse as the Android apps can't deliver the revenue that was thought would be there based on those market share numbers. Right now their budgets are based on business models from last year that don't seem to be coming true.
What happens if an iWatch is created and it is a hit? The ecosystem gets stronger, and the developers get more focused on iOS. Then the ecosystem gets stronger. Consumer have more synergies from staying in ecosystem because the best app run across all their devices. Then the ecosystem gets stronger. Apple TV becomes more useful and all your devices work with the $100 devices connected to your TV. The ecosystem gets stronger.
You can see how this plays out over the next two years, right. I'm not saying I know this for sure. But it doesn't take too many leaps and assumptions to get the point I'm making.