According to the prophecy Cersei will be killed by the Valonqur, High Valyrian for Little Brother. There are those who argue that it might not be gender specific.
For the successful resolution of this question, it is necessary for Cersei to be killed and for it to be clear that this is fulfilling the prophecy as said. If it is on the basis of an order it may be accepted, even if it is not done by that person personally.
The identity of the Valonqur will hence be determined based on Cersei's death.
In the case that these conditions are not met, the question will be cancelled and all wagers will be refunded.