Apple's iPhone OS was initially made to run on the iPhone only. Then, over the past few years, Apple has introduced the iPod touch and iPad, both running on the iPhone OS. The only problem is, that the iPod touch and iPad are not iPhone's.

iPhone OS  is a very specific name for the operating system of an iPhone, not iPod touch or iPad. Now, I don't think Apple will be naming their OS' iPod touch OS and iPad OS, but I do think they need to think of a more general mobile operating system. Maybe OS X Mobile?

I don't expect to see it happening at WWDC tomorrow, but I think it might happen sometime in the near future.