I respectfully disagree. I don't think there's some feature that is enough to dislodge Windows. I think it's going to take something like iOS on the desktop.

By that, I'm not really talking about the touch-based UI (although that's part of it). I'm thinking about the app model. The model used by Windows is too complex (and Linux is even more so).

There are a lot of things Apple got right with iOS, but I'm especially fond of the security measures. Apps are sandboxed, they hide filesystem details, inter-app communication is mediated by the OS, and updating happens mostly transparently. The tight integration between iOS and the hardware for security reasons is also something that should be copied but will be difficult to do.

As a software developer, I couldn't use something like that to do my work, but most of the non-developers in my life could. Microsoft's current approach where they half-ass everything isn't going to work (IMHO). They are in no real danger though, because nothing else is challenging them today.

Potential challengers are around though. Apple is pretty close with the iPad Pro. Valve's Steam box is also on that path.