Sure, the dude is petrified for now, but the Five want to bring him back (only to kill him for good). This plan seems shaky at best. We’re wondering why Qetsiyah doesn’t just put in an appearance and kill her ancient crush so she can be with him forever. She has the power!
The second-to-last time we saw Esther, Alaric (Matt Davis) had just staked her and Klaus was whispering to her dead body that he’d won and he’d build an army against her if she ever came back. (The last time we saw her, she finalized her plot to turn Alaric into an unstoppable killing machine.) Here’s the thing: This witch is not a fan of her children. If you recall, she tried to kill them all. We doubt she’d return to Mystic Falls to help them stop any kind of threat. Should Silas — or all the hybrid, hunter, and witch ghosts who are in Mystic Falls right now — kill them, it would be doing Esther a favor.
Then again, if Qetsiyah did come back for Silas, seeing her and Esther do battle would be pretty epic. Maybe a little more time on the Other Side has mellowed Esther out?