Hermione's Parents

We here very little about them... will they be key to the plot in DH? no one knows for sure but I think that they could be killed off farely quickly by J.K. it would dampen Hermione's spirits and that would be good for Voldemort wouldn't it? To kill someone close to someone who is helping Harry would be good for Voldemort right? Well we don't know but maybe they could be the secret to unlocking more about Hermione we could still find out more about her. They could definetly be important in DH but we can't be sure this is just another one of my theories.