This years WWDC app is looking much more flat don't you think? This aligns with the rumours that iOS has been undergoing a overhaul with Jony Ive in charge of the process to make everything much flatter.
2011 and 2012 WWDC App
The 2012 version clearly went much more minimal from the 2011 version, much like some parts of iOS 6 did, however plenty of Apple's regular styling still remained.
2013 WWDC App
While the 2013 version looks pretty similar to the 2012 version, it drops all the remaining gloss and shadows, most noticeable on buttons and some of the text.
Also check out the icon, where is the usual gloss that we see on Apple's app icons? While not using a completely flat colour it is much more flat than what Apple usually does.
Whatever Apple actually reveals is uncertain but design suggestions in a few app such as Passbook and Podcasts also strongly suggest the flat design move.