"It was born out of purely creative reasons," producer David Heyman told the Times. "Unlike every other book, you cannot remove elements of this book."
The two final "Potter" films will be shot concurrently, much like the blockbuster trilogy based on J.R.R. Tolkien's epic fantasy novel "The Lord of the Rings."
Another famous Tolkien tome, "The Hobbit," is also being split into two live-action movies set for back-to-back shooting to begin next year.
Filming on the sixth "Potter" flick, "Harry Potter and the Half-Blood Prince," began in September.
"It's been brilliant," said star Daniel Radcliffe. "It's also, I think, the funniest of the films so far."
The "Potter" film franchise has pulled in $4.5 billion at the worldwide box office.