So, I guess we've got Korra
with us until 2015? That's assuming one book per year. If that's the case, that's a good run.
Korra's outfits don't look all that different from what she already has. I liked seeing her in the more modern civilian clothing from Book One and I wouldn't mind it if she adopted that style at some point.
Asami's concept art looks good.
Asami's Corporate Outfit
Asami's Pilot Outfit
And Mako's outfit looks like a Starfleet uniform variant at first glance.
Mako's Starfleet Uniform