I was selected to participate in the Battlefield 4 Community Test Environment on Xbox One as I'm in the Xbox Preview Program and have BF4. I had to take a survey to Opt in which I did a week ago, but I still haven't had a message with a code.
They said they are doing it weekly for invites. They want new blood flocking in in waves. Was somewhat a ghost town last time I played. But there was a 30GB update patch I didn't install yet.