Android 4.0 Ice Cream Sandwich was only just launched in late 2011 although it is only available on a fraction of devices that are available for some reason. The reason DigiTimes believes Android 5.0 is launching early is due to a release of Windows Phone 8 and wanting to beat them out of the gate so to speak. Also, an interesting quote is found on DigiTimes which discusses the OS pushing for dual-operating systems... ie, a mix of Jelly Bean and Windows 8 on the same device.
Android 5.0 will be further optimized for tablet PCs, while Google will also integrate its Chrome system functions to push dual-operating system designs. Brand vendors can either choose to adopt only Android 5.0 or add Android 5.0 to Windows 8 devices with the ability to switch between the two OSes without the need to shut down the computer.
In my opinion I believe that Google will follow its yearly pattern of launches. In the beginning, Android was constantly updated which led to a lot of fragmentation. They then decided to slow down major releases to be more in line with a yearly cycle. With that in mind, expect Google to release a Nexus device in November/December 2012 which will also have Jelly Bean installed.