The Australian tech site, Smarthouse, has reported that Toshiba is working with Microsoft on a new version of the Xbox 360. Developed in response to the PS3, this new Xbox would include an internal HD DVD drive, larger hard drive and new entertainment software.
Microsoft, according to insiders at Toshiba owner of the HD DVD patents, claim that Microsoft is working on a brand new Xbox that will incorporate not only a new HD DVD drive but a large hard drive and new entertainment software that is a spin off from its struggling media centre offering.

The device is being developed in response to the PS3 driving sales of games software and Blu-ray content in several countries. A recent Sony Brand Wave study conducted in five countries including the UK, Australia, France Germany and Spain revealed that a key reason that consumers are buying a PS3 is because it includes a Blu-ray player.
While Microsoft has denied in the past that they are working on an HD DVD equipped Xbox 360, I would not be surprised if one was in the works. Hopefully they can get it out on the market before the format war is over. If you'd like to read more, the entire article can be found here.