At WWDC 2013 Apple unveiled OS X 10.9 Mavericks and released Mavericks Developers Preview. Mac OS X 10.9 Mavericks is packed with a lot of new features so in following you can find the system requirements and list of compatible Macs with OS X 10.9 Mavericks.
OS X Mavericks System Requirements
Macs must have a 64-bit Intel CPU and an advanced GPU to run OS X 10.9
At least 8GB of available disk space required for installation
An internet connection is required to download OS X Mavericks.OS X Mavericks Supported Hardware List
iMac (Mid-2007 or later)
MacBook (13-inch Aluminum, Late 2008), (13-inch, Early 2009 or later)
MacBook Pro (13-inch, Mid-2009 or later), (15-inch, Mid/Late 2007 or later), (17-inch, Late 2007 or later)
MacBook Air (Late 2008 or later)
Mac Mini (Early 2009 or later)
Mac Pro (Early 2008 or later)
Xserve (Early 2009)
There is a possibility that o enjoy full fledged essence of OS X 10.9 Mavericks new features you may require a completely new and latest Mac system.
See also:
Mac OS X 10.9 Mavericks Developer Preview 1 Released
iOS 7 New Features
iOS 7 Beta 1 Released to Developers
iOS 7 Compatibility and Availability