Harry Potter Book 7

It seems to me tht Harry Potter Book 7 is going to be the longest and no doubt the most exciting book of them all! I have a feeling something awfully strange is going to happen. A few days ago I came across an interesting theory- In the 28th chapter of Harry Potter and the Half Blood Prince(The Dutch Version), at the end of the letter to the Dark Lord, R.A.Z is mentioned. I am not that sure but here "Z" might stand for "Zwarts" or Black. it says so in a column of "The Pensieve". But who knows what surprise J.K.Rowling might spring. Does anyone else have theories to share??