Possibility to output the video to a virtual webcam device similar to Dxtory's DirectShow output. Most likely as a streaming mode or as an output in addition to RTMP/File Output Only.
Practical implementations could be streaming to Skype or Flash applications, uploading straight to YouTube using Webcam Capture
or even livestreaming on YouTube using Google+ Hangouts.
Think this could be really nice, I can't think of any other way to get OBS to a webcam device that doesn't suck.