Personally I think Elspeth might come back as W/B, Elspeth the Returned. Zombie walker!
When mortals die in Theros, they go to the Underworld. The living can only speculate what the Underworld is really like, because the Returned reveal nothing.
If there are more obstacles waiting for Elspeth, she will face them unhindered by mundane cares and concerns, more powerful than ever before. [x]
People are speculating that Elspeth may return and replace Heliod as the white god of Theros. The gods are created by devotion, and right now Elspeth has nothing but it while Heliod is out of devotion after killing his own priests. So who knows, our beloved Planeswalker may not be out just yet…