There is a lot of prognosticating about the future of Mac OS X, in the light of the stunning success of iOS that runs on iPhones and iPads. Many people are guessing that the Mac laptops and desktops (if they even survive) of the future will run something like iOS, and not OS X.
There are lots of reasons why iOS is superior to Mac OS X. iOS is immersive, focused, simple, and intuitive. There is no need of a mouse and its distancing effect (you're moving this small brick thing, which moves a cursor, which you can then use to interact with the things on the screen), as you simply press the things you want to happen. There's also this wonderful exploratory nature of iOS; manuals are largely gone, and you discover what things do and their features through play and experimentation. This is part of the joy of these devices, and why they are so personal, in that they invite you to discover them on your own, without a daunting manual or difficult system of options and inputs. You don't have to worry about breaking it, since the operating system and its files are hidden from you; you can't accidentally delete the system files or something. You can't even delete the standard iOS apps if you wanted to. Apps can be easily re-downloaded, and most all problems can be fixed by the mystical iOS reboot. The real fear is dropping it, the cost of replacing it, and the data that's on it (though with iCloud and the cloud in general, the last is greatly mitigated). iOS and especially the iPad are the computers we wanted decades ago, when they were buggy, slow, and difficult--installing a printer was a chore, setting up a machine was frustrating, and virus/malware stymied the most hopeful family member from really enjoying the WWW. So the power of iOS, and its astronomical growth, is obvious.
But I can't see OS X really going away. I'm typing this in OS X right now, with two monitors and a full keyboard at work, and I can move my eyes between multiple windows and screens. The benefits of iOS--its speed, immersive screen, size, and little weight--are also its downfall, as you really do need a separate, tactile keyboard to do serious work (as Harry McCracken discusses, with Katie Floyd and David Sparks), you can't work from multiple windows and screens simultaneously, and you can't use apps in direct conjunction with each other (such as, you can't use 1Password to fill in your address via an extension to the browser [yes, you can do this from the 1Password browser itself, but it's a bit kludgy]). It's a mono-tasking world with iOS, and that has its benefits, but do we really work one application and screen at a time? In writing and researching, I'm flipping to the internet and PDFs and notes and research in various applications. I'm moving from notes and texts to email responses. This is not as fast and fluid on iOS. Yes, you can multitask between apps on iOS, but it's still successive, not conjunctive. You have to cumbersomely send files between applications, and flip back and forth across various windows, instead of a seamless synchronicity of multiple windows and applications.
So, here's to multitasking, not in the distracting mode (where you're on facebook while writing, which never works) but in the conjunctive working mode. Here's to multiple windows and screens when it's what you need. iOS is great for travel, portability, checking in, or doing those things that are immersive and naturally monotasking, but to really get to work on the farm, you need a truck.