A new addition to Apple’s current MacBook line-up is rumoured to be in the works in the form of a 15-inch laptop inspired by the ultra-thin chassis of the MacBook Air.

Apple Insider reports that the 15-inch laptop is near to the end of its testing phase and could make an appearance in 2012, but as a next-generation MacBook Pro model rather than an extension to the MacBook Air series.

The new slim model is rumoured to come without a DVD Drive, but would include many of the features of the MacBook Pro, such as a backlit keyboard, ThunderBolt high-speed ports, an SD card reader, USB, audio and Ethernet.

Apple has recently overhauled its MacBook Pro line-up, equipping all models with Intel’s performance-enhancing Sandy Bridge processor as well as more storage space and a new AMD Radeon graphics card.

It’s unclear, however, whether Apple would wait for the arrival of the Ivy Bridge chipset, rumoured to be released in the first half of 2012, or launch this new model as soon as possible, using the current Sandy Bridge processor. Either way, it looks like the MacBook Pro range is set for a design overhaul, which could possibly spread to the 13-inch and 17-inch models.