On Sunday night, the final episode of the HBO's "Game of Thrones" will air. This has been the highest-rated season in the show's history, with last week's episode watched by 18.4 million people, its most massive audience ever.

With numbers like that, it would seem that the series is going out on a high note, which is good news for the upcoming HBO prequel series, "Bloodmoon." It would also seem to indicate robust sales of future home video editions and of the "A Song of Ice" and "Fire" book series upon which the series is based.

Unfortunately, many longtime fans have been unhappy with this season, and they haven't been shy about saying so. The outrage isn't limited to the fan community either – such mainstream publications as Forbes and The Washington Post have run pieces that are highly critical of the way the show is winding down.

The outrage has even inspired a Change.org petition called "Remake Game of Thrones Season 8 with competent writers," with over half-a-million signatories and climbing.

Clearly, some have decided that it's time to take to the streets with torches and pitchforks. So can the franchise withstand this level of ire?

Representatives for HBO could not be reached for comment, but Barna William Donovan at the Department of Communication and Media Culture at Saint Peter's University said alienating fans could indeed put the franchise in danger as a commercial force.

"If audiences are left as angry once the final episode has aired as they are now, any future plans for spinoffs and DVD sales could very well be in jeopardy," he said. "Fan communities do not like to be let down by long-running franchises, and they have often shown that they are willing to walk away from entertainment that disappoints them."

The numbers show that fans will eventually tune out a franchise if it disappoints them enough. 1979's "Alien" was a surprise hit that grossed $283 million at the domestic box office after adjusting for inflation, but the franchise bottomed out with 2007's "Aliens Vs. Predator - Requiem " faring the worst at $53 million after inflation. This also holds true for the Terminator franchise, which dropped from the "Terminator 2: Judgment Day" franchise high of $438 million after inflation to $98 million for 2015's "Terminator: Genisys. "

Donovan added that if the finale leaves a bad enough taste in viewers' mouths, it could be detrimental to another beloved franchise. Series creators David Benioff and D.B. Weiss have been tapped to create the next trilogy of "Star Wars" films, and Donovan believes a disgruntled response to "Game of Thrones" today could jeopardize "Star Wars" tomorrow.

"There is already a faction of 'Star Wars' fans who were unhappy with last two entries in that franchise — 'The Last Jedi' and 'Solo: A Star Wars Story' — because they felt the films strayed too far from what they originally liked about the series," he said. "So having Benioff and Weiss take over the franchise might further alienate many 'Star Wars' fans."

Of course, all is not necessarily lost just because a series doesn't end the way fans wanted it to. The HBO series "The Sopranos" had a famously unpopular final episode, yet the prequel movie "The Many Saints of Newark" is set to debut next year. "Seinfeld" ended on a notoriously dissatisfying note for many fans, but that didn't stop Hulu from buying the streaming rights to the entire series in 2015 for a reported $180 million. It also didn't stop series creator Larry David from having his own popular HBO show, "Curb Your Enthusiasm," just two years later.

Still, Andrew Selepak, director of the Master of Arts in Mass Communication Program at the University of Florida, said Benioff and Weiss have reason to be apprehensive about the future.

"While David Benioff and D.B. Weiss were once seen as geniuses for how they were able to adapt George R.R. Martin's books to the screen, now they are seen by some as incapable of telling a story and only capable at repurposing someone else's vision to the screen," he said. Only time will tell if that impression will last among that subset of fans.

Not everyone has such a pessimistic take on the situation. Blake Masters, the creator of the Showtime series "Brotherhood, " said that he doesn't expect today's fan reaction to do any damage, in part because of the influence of "A Song of Ice" and "Fire" author George R.R. Martin.

"So as long as they see the prequel as bearing Martin's authorial stamp, they will eagerly tune in," he said.

Gino McKoy, director and screenwriter of the upcoming science fiction movie "Lumina," said that the angry response to the final season is actually a testament to the franchise's long-term viability.

"The outspokenness of 'Game of Thrones' fans speaks to the success of the franchise," he said. "The buzz this final season creates will help cement its place in entertainment history because the controversy triggers curiosity."

Daniel Barber, chief strategy officer at the Tangent Agency, agreed. Barber, formerly of Legendary Entertainment, worked with such franchises as "Pacific Rim" and "Godzilla," and he said that controversy is simply an expression of how engrossed the fans are.

"The opposite of cheering isn't booing – it's silence," he said. "Whether fans love 'Game of Thrones,' or love to hate it, they're hyper-engaged. The same fans who voice their outrage are likely the very same who'll be first in line for the new series, books, DVD collections, and whatever else comes next."

With one episode left before the series becomes a part of television history, it remains to be seen how fans will respond when the final credits roll. For Barber's part, he expects the ending to be as divisive as ever, something he said fans should have seen coming all along.

"'Game of Thrones' wrapping up with all fans smiling was never an option," he said. "As Ramsay Bolton said, 'If you think this has a happy ending, you haven't been paying attention.'"