Even if the writer remains in the UK, she is likely to reach billionaire status in her early sixties, making her the first author in the history of literature to make such a sum from her works.
Financial experts say that with an estimated 280 million already in the bank, the 37-year-old author is destined to boast a ten-figure bank balance within her own lifetime.
Indeed, if Rowling were to avoid tax by leaving the UK and living in a tax haven such as Monaco, she could become a demi-billionaire in just five years’ time, at the age of 42.
Rowling’s earnings potential has emerged just days before her income will be boosted again, with the publication of the fifth book in her series about the bespectacled boy wizard.
Harry Potter and the Order of the Phoenix will go on sale at midnight next Saturday (21 June), and has been described as the most pre-ordered book in history. Bloomsbury, the book’s publishers, have printed an estimated two million copies, and the online bookseller Amazon.com has received more than 875,000 orders worldwide since it began promoting the book.
Rowling has already made an estimated 280 million from the first four Harry Potter books - Philosopher’s Stone, Chamber of Secrets, Prisoner of Azkaban and Goblet of Fire. The tales of Harry Potter and his adventures at Hogwarts school have sold 200 million copies in more than 40 different languages. According to the Sunday Times Rich List she is now wealthier than the Queen, with half her earnings believed to come from the two Harry Potter films and merchandising rights.
The woman, who six years ago was living on state benefits as a single mother in rented accommodation in Edinburgh, can look forward to seeing her income continue to explode.
A total of three more Harry Potter books are planned, including Order of the Phoenix, with each book in line to become a cinema blockbuster.
Financial experts consulted by The Scotsman have estimated that Rowling could reasonably expect to earn an extra 50 million annually for the next seven years, from book and film receipts. Soon afterwards, the author is expected to benefit from the generational effect - the point at which people who loved Harry Potter as a child begin to buy her books for their own children. One expert suggested this could easily garner Rowling 12 million a year.
Scott Morton, a principal consultant with KPMG in Glasgow, said: "JK Rowling can definitely become a billionaire.
"When that happens depends on how she invests her money, how long she lives and what happens to Harry Potter in the future - but there seems to be little doubt about that.
"I think we can bank on JK Rowling becoming a billionaire."
If the author remains resident in the UK, paying the top income tax rate of 40 per cent, she would need an average annual return of 6.2 per cent to turn this future income and her current 280 million into 1 billion by the age of 63, allowing for inflation at 2.5 per cent.
Fergus Hinchliffe, a senior financial planning consultant at Grant Thornton, said that even if Rowling wanted to minimise risks, there is no doubt she can become a billionaire within the 80 year life-span of the average UK woman.
"There is no doubt JK Rowling could be a billionaire. A range of cash holdings, fixed interest bonds, government bonds and corporate bonds should achieve this, without high risk."
Richard Laverick, the head of tax at Ernst & Young in Scotland and Northern Ireland, said: "Unfortunately, with such a level of income, it is difficult to avoid a 40 per cent tax charge. So long as she is resident in the UK the majority of her income will be chargeable at 40 per cent."
News of Rowling’s future wealth is no surprise to those in the world of books.
Giles Gordon, of the literary agents Curtis Brown, in Edinburgh, said that he could think of no other author in history who had achieved such earnings or who could reasonably expect to.
He said: "Go back as far as Chaucer, go back as far as Shakespeare, and you will find nothing to compare to what has happened with Harry Potter.
"Even my client Ian Rankin, [the author of the Inspector Rebus detective thrillers], who has sold millions in many languages, can be seen as poor by comparison to JK Rowling.
"Harry Potter is something way beyond the world of literature. It is a cultural phenomenon that has gripped the world. It is like an eclipse of the moon.
"Even this morning, as I took my nine-year-old daughter, Clare, to school, she was saying: ‘Well, only nine days until the next Harry Potter is out.’ It is extraordinary."
But fans who live in hope of catching a glimpse of Rowling on her way around Edinburgh or close to her Perthshire retreat, need not fear she is about to leave her adopted land.
A spokeswoman for Rowling said the author never comments on her earnings, but indicated that she is not seeking out a tax haven in a bid to achieve billionaire status.
She added: "JK Rowling is very settled in Scotland and there is no indication that is likely to change. Scotland is her home."
Scott Morton said that whatever investments Rowling made, it was unlikely she would find a return to match that offered by her own talent, with decades of creative life still ahead of her.
Mr Morton said: "She has made many millions in just a few years. Her safest investment would be to write more books. JK Rowling’s best investment would be in herself."