Sources have described iOS 7 as “black, white, and flat all over.” This refers to the dropping of heavy textures and the addition of several new black and white user interface elements.
Sources say that over the past few months, Apple has re-architected iOS 7′s new interface several times, so until the new software is announced at WWDC, interface elements could dramatically change from what Apple has been testing internally in recent weeks.
We finally have a bit more on the details of feature set expansion:
the latest iOS 7 builds being tested include new panels for quick access to information. For example, in addition to local weather and stocks information (like as introduced in iOS 5), Apple is testing other widgets for Notification Center. Sources shared examples such as localized news feeds. Additionally, Apple is testing a dedicated, easily-accessible panel for WiFi, Airplane Mode, and Bluetooth toggles.
In addition, all Apple-designed core applications such as Mail, Calendar, Reminders, as well as Game Center, Notifications and the Weather app have received flat treatment.
Thankfully, the same article offers some indication as to what to expect during upcoming WWDC conference next month:
While the new interface will be a major change for consumers, sources say that iOS 7 is also an ambitious update for developer-focused features.
All of that makes the waiting more exciting. Black is always sexy, but on top of that flat components arguably consume less processing power to render, therefore I would expect a more streamlined iOS7 performance across the board.
I strongly recommend to read the article in full length, as it goes in great details about what is believed to come to iOS soon.