War for the Planet of the Apes brilliantly wrapped up a very close to a perfect story arc, but 20th Century Studios is still planning a fourquel. Though it's hard to imagine where the series would go after a Caesar sacrificed himself, it could still work.
But Apes isn't the only trilogy that should continue, and many Redditors have fought valiantly for their favorite trilogies and given great arguments as to why they should become quadrilogies. Between John Blake continuing Bruce Wayne's legacy, Vincent running the Corleone family business, and Danny Ocean coming back from the dead, these ideas could work.
Ocean's
IAM-French is dying for Ocean's 14, a proper sequel to the original Ocean's trilogy, which includes a couple of the most entertaining heist capers of the 21st century. There was technically a sequel, Ocean's 8, but while it did feature characters from the original trilogy, Matt Damon was edited out of the final cut, and it was just as much as a soft reboot.
There could be a crossover sequel that combines the best of Danny's team and the best of Debbie's team, and it could see them returning to Vegas for one giant heist. However, an Ocean's 14 is ultimately unlikely, as the final shot of Ocean's 8 was of Danny Ocean's burial, but it could always be another one of his schemes.
The Dark Knight
Christopher Nolan's three Batman movies are the best superhero movie trilogy ever, and it features one of the most accomplished story arcs that span a number of films. And the ending of The Dark Knight Rises is engineered so that it'd be impossible to make a direct sequel about Bruce Wayne, but at the same time, it perfectly sets up a brand new series.
Mikeweazy explains that a fourquel should follow John Blake, the Gotham police officer who found the Batcave in the very final shot. The Redditor posits, "It can be called The Dark Knight Legacy and will focus on how he lives up to the first Batman." Nolan gave Warner Bros. the perfect jumping-off point to continue the series and potentially turn it into a live-action adaptation of Batman Beyond, and it isn't too late.
Before
Movie trilogies tend to be blockbuster franchises that make hundreds of millions of dollars, but one that often goes overlooked is the small-budget indie series, the Before trilogy. Each film was released almost a decade after the last, and they each chronicle the same couple's relationship nine years apart.
The first movie, Before Sunrise, sees the couple first meet in Europe, and the third movie, Before Midnight, sees them 18 years older with children. It's like a deeper, more philosophical This Is 40. Reddit user Tregorman wants a fourth movie in the series, noting, "The Before trilogy should get another (Before Noon?)" In fairness, it'd be right on time, as it has been nine years since the last entry in 2013's Before Midnight.
Rush Hour
Rush Hour might be considered one of the worst action franchises, but there's no denying how great Christ Tucker and Jackie Chan are on screen together. Chan's stuntwork and Tucker's comedy are a match made in heaven, and TheSonsOfBatman wants to see it one more time. The Redditor wonders, "I don't know why it hasn't happened yet. Just get a director like F. Gary Gray or Jon M. Chu to take over."
However, according to Chris Tucker, Rush Hour 4 is happening, but he's been saying that for years. Tucker first announced Rush Hour 4 in early 2018, and in early 2019, he said that Chan was committed and that it was close to coming together. But three and a half years after that, there hasn't been a single update.
Evil Dead
MarsOG13 wants to see a follow-up to the original Evil Dead trilogy, but they admit, "I know it won't happen though." A fourquel in the horror-comedy series could be brilliant, as Army of Darkness, the third movie in the series, saw Ash (Bruce Campbell) transported to the future right before it cut to credits. An Evil Dead set in a dystopian future is the Sam Raimi-directed movie fans would kill for.
An Evil Dead 4 has come close to entering production several times, and it's one of Raimi's many unrealized projects, as the filmmaker planned to make it after Spider-Man 3 wrapped filming. Unfortunately, it never happened. However, it isn't like Evil Dead content is scarce. A terrific remake was released in 2013, Campbell reprised his role for the TV show Ash vs. the Evil Dead for three seasons, and the actor even referenced the iconic character in the recently released Doctor Strange in the Multiverse of Madness.
The Godfather
The last fourquel people would expect is The Godfather Part IV, as it's a classic trilogy that tells the story of the rise and fall of Michael Corleone. And though The Godfather Part III is polarizing amongst fans, it neatly wrapped up the story. However, PhillipLlerenes wants to see the fourth movie, positing, "I know....I know...but hear me out... what is the next generation of the Corleones doing? How does the Mafia survive in 2019? I think it could be interesting."
While it isn't exactly what the Redditor is saying, there were plans for a Part IV, which followed Vincent as he took over the head of the family after Mary's death. And now is a better time than ever to produce the follow-up, as The Offer, which is a Paramount+ series that's about the making of the first movie, has drawn more audiences to the franchise.
Spider-Man 4
Sam Raimi is one of the luckiest filmmakers working today, as he has managed to spearhead two whole trilogies with (almost) no studio interference. However, he also has the worst luck, as he was unable to make fourquels to those trilogies, even though he tried so hard. Raimi has spoken several times about his plans for Spider-Man 4, most notably that Bruce Campbell was cast as Mysterio.
But Eharper9 thinks the movie can still happen, explaining, "Give us an older, more experienced Spider-Man for the 4th one." After Toby Maguire reprised his role in Spider-Man: No Way Home, and was easily one of the most exciting parts of the movie, fans want Spider-Man 4 now more than ever.
Austin Powers
Mike Myers is due a comeback, and as his newly released Netflix series, The Pentaverate, has been universally negatively received, the best vessel for the comedy actor to return is the time-traveling groovy superspy, Austin Powers. And this Reddit user thinks a fourquel to the James Bond spoof series could be great, arguing, "With Scott becoming evil, I have no closure for the series. Plus, it's been long enough for them to make some timely social commentary."
It'd be hard to make a social commentary given that Austin Powers travels back in time in each movie, but to keep the series fresh, the fourth movie could see him travel forward in time. And if Austin Powers 4 never happens, Myers should at least give fans Wayne's World 3.