The next version of OS X will be inspired by iOS 7 in some capacity, but in order to understand where 10.10 is headed, we shouldn't forget the ways in which iOS 7 itself differed from 6.
The focus has been on multiple planes of activity, where each app takes feels like a part of the system, yet true to its own cause. Even if you turn on the 'Reduce Motion' switch in Accessibility, the U.I still creates this story as each plane dissolves into one-another when you switch between them, almost as if they've been edited like a film. It's a tiny detail, but it really does "just work" and has a good calming influence on the content.
This design was integral to iOS because of the combination with the hardware; full-screen apps that are controlled with gestures. OS X, whilst still essentially a computer of sorts, is a completely different beast all together. Apple I'm sure are well aware of this, and with the number of different inputs (and outputs) available, they're not going to begin adding iOS-style effects just for the sake of continuity. Why would Apple add translucency to windows when it's only seen on Notification Centre/Control Centre? Why would they make the windows all white when many people deal with multiple levels of content all on a single screen at the same time? 'Mock-ups' like these are just the work of people who spend too much time in Photoshop, imagining what looks different.
The way I see it is that because productivity is such an important feature of Mac's, they're going to keep a lot of icons and labels in pretty much the same order, so that long-time users can still recognise these cues off the bat. The professional market is important to them, and if they've invested in a whole new Mac Pro, then they're absolutely going to want to make sure that the operating system for it equals the hardware. Otherwise, what's the point?
Regardless, some changes that I think will definitely be made.
- The dock absolutely has to go back to a 'Tiger' style. That what the cleanest one yet; the current one is a relic of the pre-iOS 7 design language.
- Window panes will be a lighter shade of grey, but certainly not white. That's just counter productive.
- Icons will retain the same proportions/shape, but updated with less colours and shading.
- iOS-style Notification Centre, but still on the side of the screen.
- AirDrop integration with iOS devices. The fact they chose to use the same name for both OS's suggests they may have had ideas.
- Finally, I can see something drastic happening with Finder. Same functionality, but could integrate with Apple's own apps a bit more.