prcscct wrote:
I would think it's a huge corporate secret that it may not be too hard to produce a phone with this capability. Whoever introduces it first will have the winner of the century. Pete

It's no corporate secret that the phones all run on essentially the same hardware, and making a device which dual or tripple boots into multiple OSes is not an issue (in fact there were some old dual SIM Chinaphones that dual booted between the older Windows Phone 6 and Android 2 around a few years back).
iOS and Windows Mobile are proprietary products. Apple will never give out a licence to a 3rd party to use its operating system so there's no way that you'll ever see iOS apps running on another device unless somebody manages to reverse engineer the APIs and make some kind of abstraction layer (not likely to happen).
Windows mobile is licensable so it's possible a manufacturer would make a device which dual boots between Android and Windows 8 RT (providing Microsoft don't have any licensing restrictions to prevent this happening) and I remember seeing news about a tablet which was planned to do just that, but I think you're overestimating the potential market for such a device anyway. People don't want to restart their devices and boot into different ecosystems just for the sake of running the odd app that isn't available on their main OS - they're much more likely to just go without. Then you have the problem of duplication. Most of the apps you have on one OS would be duplicated on the other, but as the OSs have different methods of storing data, there'd be no way to sync between the two Operating Systems other than where the app specifically supports it. Your SMS conversations would be split between the two different operating systems, depending on which one you were running when you sent/received a given message. Possibly emails too, depending on what type of account you have. You would need to manually duplicate all the info in your contact lists, your website favourites, news feeds. Then there's the memory (human) and time issue. You'd need to remember yourself which OS you prefer/need to boot into to perform a particular function, and be prepared to go through a lengthy boot process every time you switch.
Really, there are only two types of people I see such a device appealing to: app developers, and hardcore geeks who like to do things "because they can"