The steampunky/faux-Victorian tech angle looks good, though the goofy announcer is seriously annoying. It also looks like they are emphasising the humour in this trailer over the more dramatic stuff.
The Legend of Korra is set approximately seventy-five years after the previous series and charts the adventures of Korra, the latest incarnation of the Avatar, someone who is able to use all four elemental forms of magic (most magic-users - 'benders' in the setting's unfortunate parlance - can only use one). The series is set in Republic City, where technology and science exist alongside magic, and the principle storyline revolves around an anti-bending society known as the Equalists attempting to stamp out all use of magic.
The series will initially comprise a twelve-episode first season, with a fourteen-episode second season already in production. The series is expected to debut on Nickelodeon in the USA this summer.