I've heard a lot of speculation over the years that perhaps someday, Mac OS X and iOS will combine. After all, wouldn't this simplify Apple's product portfolio while streamlining their overall software experience? Well, if you ask me, the answer is NO.
Computers and phones are different. While today's phones are certainly much more computer-like than anything in the past, the fact is that the way we use computers is still very different from the way we use phones. Most of the tasks we use phones for tend to be brief and casual - send a quick note, check the time, look up an order number, or glance at the news. Computers, meanwhile, are tuned to enable in-depth projects that require hours (or years) of concentration.
Mac OS X is the perfect interface for Macs, and iOS is the perfect interface for iPhones. If you shoehorn them into a single product, you get a jumbled mess like Windows 8 (whose adoption rate was actually lower than Windows Vista). Why would you take a confusing combination of multiple user interaction paradigms, and use that to replace the perfect system you already have?
I certainly don't mind if individual features get inherited back and forth between Mac OS and iOS, but in my opinion, they should stay separate.
What about hardware? A related rumor is that maybe someday Apple will make Macs that run on A-series processors, which Apple currently makes for its iOS devices. For the time being, I am not a fan of this idea either.
First of all, Intel processors are just plain good PR for Macs. Here's what a sales pitch for Macintosh might have looked like in the olden days:
"Yes, the Windows machine has a 900 Mhz processor, and the Mac only has a 700 Mhz processor, but see, the Mac uses a reduced instruction set architecture on a PowerPC processor, whereas the Windows machine has a more complex ISA, which means that the Mac actually gets some types of tasks done faster. If you want to run Windows on a Mac, you can buy a handy emulator, which is almost as fast as just calculating the bits by hand."
"The Windows machine has a fast 2.3 Ghz processor. So does the Mac. If you want to run Windows on the Mac, you can."
I think it's pretty clear which one is the easier sale.
But besides that, A-series processors are designed to be ultra-portable and minimize resource usage, and while this is exactly what you need for a phone or a tablet, a computer running on a A-series processor would currently be much slower than an Intel machine. I think it would be a mistake to decrease Macs' performance just to make them cheaper to manufacture.
I admit that there was a time when I hated Intel and was eager to tell people that I did, but now that I have seen what their modern processors can do in a Mac, I think they are definitely a keeper.
Perhaps on an intuitive level, concepts like "unity" and "convergence" sound like really good ideas. However, at least for now, I hope that Macs and iOS devices should remain two distinct product lines.