The rumors about a new DSi were true, Nintendo announced it will start shipping the DSi LL in Japan on November 21st. This new model features a 4.2" screen instead of a 3.25" one and features better battery life. Engadget reports it will be released in Europe as the Nintendo DSi XL in Q1 2010, but it's still unknown when the US will follow. In Japan the DSi LL will retail for 20,000 yen (about $221).
The above comparison is straight from the Big N showing the DSi LL vs. the white DSi. Besides the obvious increase in height and width, the 21.2-mm handheld is chubbier than the 18.9-mm DSi but slimmer than the 21.5-mm DS Lite when it ships in your choice of dark brown, burgundy and natural white. The battery seems to be roughly on par with the DS Lite going for about 4 to 5 hours on maximum brightness and intensity or 13 to 17 hours when dialing back the display to its lowest settings.
The following picture compares the size of the regular DSi and the upcoming 4.2" version: