If you want to boil down Apple’s thought process on this whole thing, it’s really about feelings. Apple cares how its users feel when using its products. When a PC user who has purchased an iPhone or iPad falls in love with the experience of using it, Apple cares about making them feel the same way about the Mac. It would be stupid if it didn’t try to make the millions of people who have purchased iOS devices feel welcome on the Mac.
That’s not the same, however, as crassly transforming one operating system into another to cash in or exert more control. The ’10 ways that OS X is being turned into iOS’ headline is easy to write, and you can’t argue with the fact that both platforms are informing decisions made in the other, but there is a distinct difference between unification and absorption.
I agree, it's not about making OSX into iOS. However, I am 100% sure that within a few years the base will be the same and we'll only talk about one OS (probably not named "X" or "iOS"). Why keep two different branches when so much is unified, it's much easier to maintain a single base than two. But OSX will not become iOS, and neither will iOS become OSX. Both will merge into one single multi-platform OS.