That's precisely what analyst Mark Moskowitz thinks Apple might be working on. Such a platform was even dubbed as iAnywhere.
Theoretically, this is quite possible. As a matter of fact, this is a direction that Microsoft is trying to pursue. So, it is quite possible that folks in Cupertino are working on the similar system.
As a side effect, this would give considerable boost to Apple on the side of innovation. As you might be aware, key shareholders at Apple are not very satisfied with the company's recent stagnation on the innovation arena.
Above mentioned is just a hypothesis. All we have to do is just wait and see if the unified Apple OS comes to reality.