Nowaday, iOS is very popular, all of iPad, iPod touch and iPhone are using iOS. There are a ton of iOS app in the market, I guess that should be over a million. I believe a lot of people think that will be great to have a laptop or desktop running iOS, As a result, all of us can have a set of same apps in our iPhone or iPad in a desktop.
I don't think that is a good idea, iOS is design for Mobile. That is aimed to low energy consumption. In desktop and laptop, energy consumption is not as important as Mobile device, the performance can be more important. Although you can say iOS and MacOS is a kind of BSD os. But iOS is for ARM architecture and MacOS is for Intel architecture. Lastly, the user interface of iOS is for touch screen, that may not be the best option in the desktop environment.
I think iOS works well in mobile and MacOS works well in desktop. That is not a easy task to merge them into one OS which runs well in desktop and mobile.