The developer preview of Lion makes it pretty clear which way things are heading. I wouldn't expect much deviation from that on the Mac side. I'll be interested to see what they're planning for iOS 5 though.

It's all marketing spin. Let's not forget the iPhone launch in 2007:

"We start with a strong foundation. iPhone runs OS X. ... Desktop class applications and networking."

Flash forward to a world that has been fundamentally changed by the iPhone and iOS, and the new marketing line is:

"The power of Mac OS. The magic of iPad." and other such lines about bringing iOS to Mac OS.

It's all about perception, reality, and marketing.