The latest design for Apple's mobile operating system might not be ready in time for the World Wide Developer's Conference this June, but when it comes it will look a lot different than the current iPhone software—the look of which hasn't much changed since its debut in 2007. The design overhaul, which will look "flatter," "fresher," but also "familiar," is so ambitious that it has caused delays, sources tell Bloomberg's Adam Satariano. But while it might not make it in time for WWDC, it should be ready for a planned September release. Here's what to expect:

1. A Flat Design

9to5Mac's Mark Gurman explains it as such: "'Flat' design is based on simplicity and pushes aside heavy textures and digital metaphors of real-life objects found in skeumorphic interfaces," he writes. Let's start with the first part of that description: Simplicity and flatness. The Windows phone has a flat look, for example:

That's considered a more fashionable design in the software world. Facebook recently flattened its logo design by removing the white bar at the bottom, for example, much to do the delight of the tech design nerds.

Apple's current icons have more of a 3D look in which they are shaded and shine. The new look reportedly will contain an all-new icon set for Apple’s native apps, reports Gurman. Here is a flat version of the current set from Andrew McCarthy, who has a full set of icons he made intended for personal desktop use here:

It's the same basic shapes and colors of the Calendar and notes apps, just without all that shading and attempts to make it look like actual torn paper.

2. Down with Skeumorpism 

"Skeumorphism" refers to the tacky visual metaphors that don't quite make sense. Apple (and others) still use it in software design, holding on to an outdated theory that people needed real-world signals to understand how to interact with computers. (Like a folder for storing documents, for example.) More specifically, it's when "objects retain ornamental elements of past, derivative iterations--elements that are no longer necessary to the current objects’ functions," as Fast Company's Austin Carr once explained it. There's an entire website for pointing out these choices. Like these leather "calendar" buttons, for example, don't really make sense. (Some say this leather stitching was based on a texture in Steve Jobs's Gulfstream jet.)

 

Gurman notes a change that has already happened in the Podcast app, which used to look like an actual tape dek:

3. New Notification Center

Gurman mentions the possibility of more "glance-able" information hubs, such as updating the Notification Center, a concept and look Apple largely stole from Android. His sources aren't certain this will come along with iOS 7, but there are a couple of concept ideas floating around that at least look pretty to me:

4. Improved Apps: Probably Not 

The look might change, but the utility won't, per Gurman. "Its core apps and system fundamentals  (like the Lock and Home screens) mostly operate in a similar fashion to how they do today," he said. Though, it sounds like Apple's working on updating some of the native functions, according to Satariano. "Bigger shifts, to such features as e-mail, may not even be ready this year and may be introduced in future releases," sources told him. At least they are working on these "bigger shifts."