There's not much to go on

[annemehr]

> Anyway, I thought Jo had stated that it 
> > wasn't a rune? Or is that my imagination?
> > 
> No idea...anyone else?

She didn't actually rule it out. It was sort of brought up during that
World Book Day chat in March '04 -- somebody was being cute:

|Cathedral: Don't want to rune the ending, but will we be finding out
|more about the significance of the shape of Harry's scar in future
|books?
|JK Rowling replies -> The shape is not the most significant aspect of
|that scar, and that's all I'm going to say!

As far as I know, that's all we know.

Jo: 
> Yup, there's a strong possibility that pride will be the thing. I 
> don't think that it will be Harry's love that does for Voldy but 
> proof of his own Mother's love which he won't be able to tolerate. 
> Voldy could have a matching scar of his own....

Anne:
I could see that.

I'm afraid there's going to be sweetness in the end.  JKR loves that
stuff (so do I, I admit), though she manages to keep a leash on it. 
But I really do think there will be a sharp edge to it -- like
chocolate-covered habaneros, maybe.  A spoonful of medicine to help
the sugar go down?

All right, sorry, I'll stop now.

Jo:
> if JKR resurects Harry 
> in the end.

Anne:
Argh! That's my nightmare.