Well, we've already seen leaks of the MBP case (from the same blog, right?), so I would say so. Obviously, it won't be as big of a change since the MBP is already in aluminum.
Overall, it seems like the entire notebook line is going with a tapered aluminum look. Seems to me like the Air, Pro, and Macbook are meaning less and less...I wouldn't be surprised if they change what designates Pro to power and performance rather than screen size and case material (obviously the latter is the same in all three cases). Thus:
Macbook Air: 13.3", no optical disc drive, lower performance, targeting the road warrior
Macbook: 13.3" and 15" options, a variety of processor/hard drive options, integrated graphics (perhaps with nVidia chipset, the IG will be better?), still targeting the consumer, student, etc.
Macbook Pro: 13.3", 15", 17" options, high end processor/hard drive options, discrete graphics processors (still potentially with nVidia chipsets), superior monitors (matte option, obviously, for graphic designers, etc.), targeting prosumers, pro users, creative designers, etc.
I realize this isn't the first time this sort of revamped product line has been bounced around before, but with these new leaks, it seems likelier than ever.