OK, so, The Unholy Consult. Wow. That was an ending. And then some.
I really can't say anything without spoilering the shit out of what happened, except I will say Meppa was nowhere to be seen. So I can only assume he has been secreted away somewhere by Kelhus and has a role to play in the final trilogy. And as the Last Cishaurim, with power enough to even wow Kelhus, I can't imagine his role being minor.