As always with Microsoft, you won't have to wait another week or two to get the answer because Engadget has already found it. A page at the German Amazon website indicates Microsoft will release a new Explorer Mini Mouse notebook mouse with "Blue Track" technology. This new technology uses a blue LED in combination with a wide-angle lens.
So what does this all mean? Basically it means you'll get a mouse with better tracking that will work on more surfaces than laser or optical based mice.