David Labrava, the real-life Hell's Angel who plays Happy, was promoted to Sargent-in-Arms at the end of last season when Jax was preparing for his inevitable trip to prison for the school shooting. Because of his larger roll in SAMCRO, fans will be seeing a lot more of Happy in the seventh season.
Niko Nicotera, who plays Rat, has also been promoted to series regular for the season. There has been a drastic shift in the power structure of SAMCRO with Jax going to prison for one thing or another, and he has already abdicated his thrown and handed over the crown in preparation. Rat has always seen Gemma has the mother of the club and has protected her in many instances, however, he really liked Tara. If Rat finds out that Gemma was the one that killed her, he may end up turning on her, or be the one to do her in.
This season of "Sons of Anarchy" is likely to be a brutal one as it is the last and there are a lot of story lines to tie up before the season is over. With Happy as Sargent-in-Arms, there is no doubt that some of these story lines will end up a mess.