So I just finished watching season 2 of Legend of Korra, and I'm certainly not done. I realize she basically did her job as avatar and saved the world. Is there a season 3 in the making? o a whole new series of a new Avatar?

Yes. Nickelodeon has ordered season 3 and 4.
Season 3 is called "Changes" and will deal with how Korra handles being avatar now that there are spirits in the physical world. It will also focus más on the Earth kingdom (yay! más Lin Bei Fong). The 4th book will focus más on the fuego nation. There hasn't been an announced released fecha yet for season 3.

Season 3 is playing right now! New episodes every Friday!