How to create Omega 4 subtheme with new "default" libSass based starterkit?
I've had a lot of problems getting started with the new starterkit. It seems to me as if omega-guard does not yet support the new kit. You can still accomplish the same by running gulp in the subthemes directory. This will start the gulp watching process in foreground.

For more information about gulp and the libSass starter kit, I can recommend this post: https://www.drupal.org/node/2537364#comment-10287771