Natural Selection 2, even though not even being released yet, already has a quite active competitive scene. There are teams, streamers, casters. Tournaments will be announced soon, especially when the release date is closing by.
The subforum of competitive talk in the official UWE forums can be found here:http://www.unknownworlds.com/ns2/forums/index.php?showforum=109
There are several youtube channels showing videos of competitive matches, one of the channels can be found under
List of currently active teams: