If I remember correctly, M$ mentioned in a press statement that they're not ruling out blu-ray support in future xbox consoles.
Sad to say HD DVD is already gone, no studios are going to support that format except Dreamworks, so no use supporting it already. But for those already have a collection, can keep it to watch.
Microsoft is even considering having Blu-ray as an add-on drive.
Xbox 360 Blu-ray player
Well, all these war is over, benefits us consumer, no need to worry which format to buy being afraid it will be phased out.