I think Mel is
almost ready to bring Jon back. Here's why... In
this scene of Thoros with Melisandre , Thoros explains how he has gotten the power from the Lord of Light to resurrect Beric Dondarrion. He says that he completely lost his faith, but when he saw someone die that he cared about, he was granted this power.
To me, that last scene of Mel turning into the old woman, showed that she is possibly losing her faith. The magic was there, but wearing off. Even
she cannot keep up appearances anymore after the death of Stannis and what appears to be confusion in what she saw in the flames. Maybe Jon's death is the last straw for her. He's the only one she saw left with any sort of power. And he's gone, too.
This sets her up perfectly to be in the same place that Thoros was in when was able to do bring someone back from the dead. So, what do you think?