If you're REALLY handy with casemods, it's theoretically possible that you could eventually rig up the older case to fit the newer motherboard. You'd have to do some serious advance planning, probably cut a lot of new holes (and fill in old ones), and find some way to securely mount the new mobo in the case. You'd also have to hope that the older screen would work with the newer mobo, too, which is hardly a sure thing.
If you're talking about just taking one motherboard out and putting in the other one, you'd have some problems on your hands. Even if you could somehow get it to fit (doubtful given the difference in battery/optical drive placement), none of the ports would be in the correct place. The new model even has some ports that don't exist on the old one (Mini DisplayPort).