Now that iOS 7 has gone to a very spare, flat look, there’s been wild conjecture about what will happen in a few weeks at WWDC 2014, when Apple is set to release a beta of OS X 10.10.

Some stories have been completely ridiculous, suggesting that  iOS and OS X will merge in some fashion. The only merging they’ll be doing is one of appearance–not functionality. OS X 10.10 will likely gain a much flatter look, much like iOS 7, but it will still have an interface optimized for mouse and keyboard.

Now, there is a possibility Apple may make the click targets larger (i.e., make buttons, pop-up menus, etc. taller) in order to support hybrid devices (laptops with touch screens, tablets with keyboards), but it’s a pretty fair guess that all the control complexity in OS X (that’s missing in iOS) will remain.

OK, so no major functionality changes, just appearance changes. But what exactly will the appearance be? Well, if you’re an iOS or OS X developer, the changes have been staring you in the face for a year. That’s because when Apple debuted Xcode 5 at last year’s WWDC, it came with a much flatter UI. The screenshots above (Xcode 4 on the left; Xcode 5 on the right) show how some–but not all–features have been flattened by removing drop shadows, gradients, and borders. Note that buttons and text fields haven’t been appreciably flattened, but segmented controls and tab bars have–not because buttons won’t be flattened in OS X 10.10, but because either Apple just didn’t get around to it in time, or they’re just testing the waters (more likely).

In addition, much like iOS 7, a single highlight color for controls is used, in this case blue. Blue tells the user that the control is a control and is clickable, much as colored controls in iOS 7 are a clue for users that they are tappable.

So OS X 10.10 will certainly look flatter, and Xcode gives us a pretty good idea of what Apple is thinking. Now we just have to wait until June 2nd to see how the rest of the UI has changed.