I sort of suspect they are leading us on a little bit with that semi cliff-hanger ending for Melisandre. I've seen some remarks from fans out in the general audience world who thought maybe she was dying or going to die when she got into bed (I don't think any of us believed that for one minute). But if that's what average viewers thought, then maybe that was the intended goal to mislead people into thinking her powers have gone out completely?
If they have her 'weak' for the first two episodes, it will really help build the tension that there's really no one there to resurrect Jon and the rumors must be wrong.
So I am not thinking she participates in whatever showdown is about to happen between Davos, the Wildlings and the Night's Watch.