Aligning with Apple’s upcoming media event on October 22, Apple is now asking developers via e-mail to begin submitting their OS X Mavericks-ready applications to the Mac App Store for the review process.
Originally Posted by Apple:
Make sure your app takes advantage of the great new features in OS X Mavericks when the world’s most advanced desktop operating system becomes available to millions of customers later this fall. Download OS X Mavericks GM seed and Xcode 5.0.1 GM seed, now available on the Mac Dev Center. Build your apps with these latest seeds, then test and submit them to the Mac App Store.
OS X Mavericks has been available as a golden master since the fifth of October, signaling that the final release is near. Apple is expected to unveil a release date for OS X Mavericks at the October 22 media event, as well as introduce a number of updates device and machine lineups.
The reason for Apple's e-mail is to try and motivate developers to get their applications ready as soon as possible to make the upgrade for users as seamless as possible without issues regarding application compatibility.
OS X Mavericks will bring users a number of new features that app developers will be able to take advantage of. Some of the notable features in OS X Mavericks include App Nap, Finder Tabs, iBooks, and Maps among others.