User blog comment:Chameleon-Guy/Predictions for the next season (after Pahkitew)/@comment-24301964-20140515203038/@comment-7985501-20140515213135

But in the end, Jo's main interactions always end up with Lightning which is why I believe if she returns, so does he. They both complete the other. TDAS sort of proved this.

Mike's most likely not coming back and Cameron and Zoey have been the main focuses for two seasons along with Mike. They concluded their story arcs at the TDAS finale. While they'll most likely return in the future, I doubt it will be anytime soon especially for Season 6. They don't have a reason to come back.