We've got the first three minutes from Book 2: Spirits online in amazing quality! Do you wait till September or watch it now?
Watch the 3 minute clip here.
The video starts with a pro bending match, featuring Bolin and Pabu giving a pep talk to two new members of the Fire Ferrets. They lose almost immediately. We don't know why Mako and Korra aren't there with him. The video cuts to Mako, now a cop, on a motorcycle chasing a car. He does some stylish acrobatics and takes the car down with firebending. Insert cheesy Mako joke. The scene transitions to Asami riding a plane. When she gets off an employee walks over and tells Asami that Future Industries is in danger of going bankrupt, and she smiles and says that everything will work out. As she walks away from him you can tell she's not sure if she believes her own words. Cut to Korra on the island, racing with the kids and causing mayhem. Korra goes into the Avatar state and wins the race.