Screenshot from Book 3: "Change" of Lin Beifong of Legend of Korra

Book 3 (Change) will be featuring much more of Lin Beifong than Book 2 (Spirits) did. Above is a screen shot of her from the upcoming season.

Additionally, Book 3 is expected to take much less time to premiere than Book 2 had taken.

[source: Bryan Konietzko's blog]