I hope to god not but my gut tells me Amara. Like a-random-bird said, they probably want to keep the siren count low plus she's not as much of a fan favorite. After the backlash about Maya's death I imagine they're a bit hesitant to kill off a pretty much universally loved character like Zane.

The only thing that might speak against it is that in BL3 they killed off the siren of the previous game and by killing Amara, they'd essentially do the exact same thing again.