A new rumor from Italy's Xbox 360 Magazine says that Microsoft is prepping an external Blu-ray drive peripheral for the Xbox 360. The external drive wouldn't work for games, and function similarly to the now dead in the water Xbox 360 HD-DVD drive.
Adding a Blu-ray option to the Xbox 360 would be a direct jab at the PlayStation 3's built-in Blu-ray functionality. The PS3 uses Blu-ray discs not only for movie playback, but for game disc storage as well. Whereas the Xbox 360 could only use it for games at this point, or would risk segmenting the userbase (remember, we're talking about Microsoft, not Nintendo).
In the past, many major releases have come under the spotlight due to the Xbox 360's inferior storage capacity in comparison to Blu-ray. One game that fits snugly on a Blu-ray disc could require 2, 3, or more of the Xbox 360's DVD format.
However, it would be surprising to see Microsoft make this late. The time to add Blu-ray would have been years ago back when Blu-ray first won the format wars. Having options available is always nice, but Blu-ray has already had plenty of time to grow. Microsoft may have missed the window of opportunity on this... by like 3 years.