I think Damon wants Elena zo badly he flips the switch so he is able tot kill Bonnie. (Like he flipped his switch to leave Enzo) Obviously, Matt, Stefan, Caroline and everybody is going to protect bonnie. That causes Stefan and Damon to be rivals again. I also think that when Damon has no humanity he will join Lily and her companions. Also I think Bonnie won't have a long life (unless they find a way around the spell) because otherwise they would have to film the final or whenever Nina joins again to be 60 years in the future, meaning it would be science fiction and I don't think they are going to do that.