iFixIt has posted their teardown instructions and photos for the new MacBook. The site even managed to take the new longer lasting battery and place it into an older MacBook successfully.
The battery looks very similar to the previous one. So similar, in fact, that it's identical in size and shape, and has the same model number (A1331).
The battery in the A1342 Mid 2010 is 65 watt-hours and weighs 355 grams. In contrast, the earlier A1342 has a battery of 60 watt-hours and weighs 347.5 grams.
Lo and behold, the new battery works in the A1342! You can get an extra 350 mAh of juice if you're willing to add 7.5 grams to your "older" MacBook.