I agree with you that what we will see is that OS X will get more iOS-like or maybe at one point there will only be iOS (or whatever it will be called then).
That day is fast approaching, with Lion being the last of the big cats, unless they're the next version of OS X will be called "Ernie Ladd" (old time wrasslin' fans know what I'm talking about).
Back on topic, I'm not a big fan of iOS, it's too limiting. OS X, while the GUI is limited, gave you access to its guts in terminal. It'll be a sad, sad day when kills OS X.