What are the odds of J.K. Rowling writing another Harry Potter book? Pretty good, actually.

Sure, it’s purely speculation at this point. Only the author knows how far that door has been left ajar in her own mind. But the available evidence and historical precedent tip the balance toward the eventual likelihood of an eighth book in the megaselling series launched in 1997 with Harry Potter and the Philosopher’s Stone.

Here is a categorical weighing of the pros and cons:

• Money isn’t everything: The most compelling argument against the eventuality of another book is that the author will never need the money. Since Rowling is not an NFL or NBA player, it is hard to imagine her blowing through her stash anytime soon.

As long ago as 2004, Forbes pegged her wealth at more than a billion dollars, ranking her as the first author ever to become a billionaire by writing books. The cash machine hasn’t exactly run dry since then. Nor is it likely to, even if she doesn’t type another word. Rowling recently unveiled a new website, Pottermore, while deciding to circumvent the publishing industry by securing personal ownership of the untapped e-book side of her empire.

Even without another book, the potential revenue streams to be generated by the existing material remains great, whether it’s in further spinoff volumes (encyclopedias, etc.) or the exponentially lucrative video game universe.

At some point, though, creative people are compelled to create. Rowling has suggested she has a couple of literary irons in the fire, while asserting that she is pursuing a path outside the fantasy genre. Whatever she produces will have an automatic audience, but what if readers come away disappointed?

“To go and create another fantasy universe would feel wrong, and I don’t know if I’m capable of it,” she has said.

Precisely. Why create another when you have one ready made?

• The pressure becomes unbearable: J.R. Tolkien was partly motivated to write The Lord of the Rings in response to public demand for a sequel to The Hobbit. Mind you, Tolkien didn’t require as much prodding as Arthur Conan Doyle, who managed an eight-year hiatus from Sherlock Holmes after killing off his famous protagonist, before finally caving in 1901 and publishing The Hound of the Baskervilles, the first of several more Holmes mysteries.

In Rowling’s case, it isn’t just readers and publishers who will keep beating the drum for another Harry Potter adventure. The movie industry, with an uncanny capacity for eventually getting what it wants, also has a huge stake.

• No extra magic required: Unlike Conan Doyle, Rowling wouldn’t need to resurrect the dead or invoke any similar suspensions of disbelief — beyond those required to buy into the existence of academies of wizardry and so on.

Don’t bet against the possibility of the mantle being handed off to a new Hogwarts’ freshman class, just as the books themselves are passed from the first generation of readers to the next.

• Even Led Zeppelin did it: After the 1980 death of drummer John Bonham, the remaining three members of the iconic rock outfit swore over and over, again and again, that they would never, ever reunite. In a music industry infamous for threadbare resurrections (the Guess Who, without either Burton Cummings or Randy Bachman, anyone?), the resolution was singularly noble.

Until they broke it, of course, by playing at 2007 tribute concert for music producer Ahmet Ertegün. Extenuating circumstances, you understand.

• Read her lips: Rowling — who has never disavowed the possibility of writing another Harry Potter but only suggested it isn’t likely — wouldn’t even be going back on her word if it turned out that Harry Potter and the Deathly Hallows wasn’t the end of the story. Quite the contrary.

In 2007, she told the BBC: “I can’t say I’ll never write another book about that world, just because I think what do I know, in ten years time I might want to return to it but I think its unlikely.”

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Last year, she told Oprah Winfrey: “They're all in my head still. I could definitely write an eighth, a ninth book. I think I am done, but you never know.”

Earlier this month at the movie premiere for Harry Potter and the Deathly Hallows: Part 2, she said: “It is my baby and if I want to bring it out to play again, I will.”

Take that as a definite maybe.