Nissan just announced details for the Japanese model of the 2013 Nissan Leaf. They're offering more features, better range, various other improvements, at a lower price of entry.
Nissan press release: http://www.nissan-global.com/EN/NEWS/2012/_STORY/121120-01-e.html
The improved range did not come from change to the battery pack. That has remained the same. Instead it came from a range of efficiency improvements and weight reduction. It's difficult to translate the range estimate from Japan, but it may be that the EPA range estimate will increase to 83 miles.