I wonder if we ever going to see anything other than Android or iOS. A third ecosystem wouldn’t be so bad.
In-between Chromebooks and generic Linux distros (say what you will about the year of Linux on the desktop, use is only growing; slow paced or not, doesn't matter), specialised Linux distros (SteamOS - you might think it doesn't matter, it's only for a handheld console, the Steam Deck, but it will force many games to have Linux compatibility. And one of the main things keeping many tech savvy users on Windows is gaming) i think a duopoly is a bit of a strong word, and it's getting disrupted.
The other is the advanced state of Windows emulation for games, you can bypass the platform effect if you can piggy back on an established platform's APIs. That's tricky though, plenty of mobile OSes tried to get traction with Android APK compatibility, but the problem with that is, why bother developing native apps for them? With games consoles it's a different situation, maybe emulation in the long term is just fine.
Meego, running on the N9, was an absolutely wonderful experience. It was smooth, fast, beautifully designed, and had simple elegant swipe-based navigation system, it had multiprocess app switching (AFAIK before iPhone OS did) and a brilliant newsfeed/notification system. It felt like it really had extraordinary potential. And Elop ditched it.