Why can't Hollywood just leave Harry Potter alone?

As the Deathly Hallows aftermath dies down, and rumours of more Potter continue, can Hollywood be trusted to let Harry fade out gracefully?

Now that the Hollywood bigwigs have had a chance to take stock and count the cash brought in by the big summer blockbuster season, rumours are rife that those big franchises either coming to a close or already finished may not be so over after all. Last week's Lionsgate/Summit deal brought rumours of more Twilight movies after this year's Breaking Dawn: Part II, but there's another big movie series that's been plagued by sequel rumours for as long as anyone can remember.
Even before J.K. Rowling had put down the pen for her last Potter instalment, there were relentless questions and speculation regarding if, or when, further stories would emerge. Chief among the questioners were movie producers hungry for more, as there's nothing more valuable in Hollywood than an established franchise. The Potter series has brought in billions of dollars in box-office receipts, and that's not even counting the DVD sales (set for a boost once the limited release kicks in), theme park traffic and other tie-ins.
The problem is, unlike with properties like Transformers or Indiana Jones, which could theoretically run and run, Harry Potter is faithfully based on a series of novels penned by an overprotective author. We'd assume any plans of making new movies unaided or unapproved by Rowling are off the table, but plans for new Twilight movies suggest that the film industry may be getting too greedy for its own good, waving aside those barriers in the pursuit of more valuable output, whatever the cost to quality.

And there are plenty of scenarios that could bring about a satisfying Potter sequel/prequel. The world has become so synonymous with our culture that it's harder to imagine a world without something waiting for release or in development. Would this be a chance for beloved plot threads, necessarily cut from the main movie franchise, to get their own film? Think X-Men: First Class as a successful template, and we may get a Marauders' (James Potter, Sirius and Lupin) movie, or a Dumbledore-centric prequel.
For fans of the books, these stories were often more interesting than whatever adventure the kids were on that week, but could a Harry-less Potter film connect with audiences as well as the 8-film series? Then there's the Star Wars prequels, which dangle the tantalising carrot of a Voldemort prequel in front of our noses. These ideas prove that, were the desire strong enough, someone could easily continue the property without straying from Rowling's canon at all, but past experiences have taught us that a franchise continued for too long, no matter how beloved, can be a huge mistake.

The much-maligned epilogue attached to the final moments of Deathly Hallows Part II was created to stop this kind of thinking, after all, and Rowling has been vocal about her desire for the story to end here. It's almost a certainty that Daniel Radcliffe, and probably Emma Watson and Rupert Grint for that matter, don't want to do any more films, which puts a damper on any sequel ideas even ignoring the soppy bookend at King's Cross station. The war was won, and the seven school years spent at Hogwarts cannot be extended.
The questions is, what was so lucrative about the Potter series in the first place? Was is Harry himself? It's doubtful, seeing as the film's poster boy wasn't exactly a classic hero, so that leaves the magical world. Children and adults went to see the brilliantly realised world that Rowling had described, but the rising anticipation for the end of an 8-film epic is what drove the final movie, by no means the best in the series, to be as mega-successful as it eventually was. If it was the prospect of a conclusion that drove audiences to their multiplex, then a further sequel would remove that aspect from any future adventures.

It's clear that there are several credible sequels, prequels or otherwise that could be brought back to the screen, but the real questions is: should they be? It remains to be seen whether franchises at the top of their game both technically and commercially, like the Lord of the Rings trilogy, will be remade in the future, but current trends for rehashing much-loved classics strongly suggests that, even if no further Potter's are made now, an all-American remake is in store for us 20-years down the line.
Greed-driven movies need to be stopped somewhere, and Harry Potter is as good a film as any to set that example. Everyone involved creatively has sworn against more movies, but the cash is still warm, and we can only wait to see whether they stay true to their words. Peter Jackson is making The Hobbit (although that's not such a bad thing), how long is it until David Yates signs on to Dumbledore: The Early Years?