In an interview with Macworld's Jason Snell, Apple's Phil Schiller, Bud Tribble, and Craig Federighi talked about the past and the future of the Mac. It's worth checking out the interview, but the most interesting part is what they say about the merging of iOS and OS X. Federighi said,
It’s obvious and easy enough to slap a touchscreen on a piece of hardware, but is that a good experience? We believe, no.
We don’t waste time thinking, but it should be one! How do you make these merge together? What a waste of energy that would be.
Federighi goes on to explain the reasoning behind these decisions,
The reason OS X has a different interface than iOS isn’t because one came after the other or because this one’s old and this one’s new. Instead, it’s because using a mouse and keyboard just isn’t the same as tapping with your finger. This device [MacBook] has been honed over 30 years to be optimal.
So while iOS and OS X clearly won't merge, Apple is still trying to make it easier for those who switch between iOS to OS X.