Kenzi will betray BoThat's why the rune glass failed, folks!
Kenzie is changingAfter whatever happened to her at the Norns, she suddenly manifest powers next season. After an episode or two of enjoying it, she will begin to change more. Bo will have to try to cure her, which Kenzie will not want to happen.
Aifie is dead.
The Morrighan fed on Vex at some point in his backstoryEpisode 3 of Season 3 revealed he actually has an artistic side beneath his Jerkass exterior, and he admits that he used to be a better man. The Slenderman-expy revealed that it is possible for Fae to feed on other Fae, so who's to say The Morrighan didn't burn him out somewhat and twist him into the guy we know now?
Bo will be feeding off of Tamsin while still persuing a relationship with Lauren
Sanctuary is in the same Universe as Lost Girl
Tamsin is in love with Bo
Alternatively, Tamsin sucks the chi out of dead or dieing warriors, killing them in the process
The mysterious Wanderer is Bo's father
Bo will save Tamsin's life...
Kenzi's past consists of her living as a Russian sex slave