It looks like to break the top 5 next year a movie is going to have to make at least $300-350M. With that in mind, let's take a look at some of the movies coming out in 2018, and some comparable movies to get some idea of how well or poorly they can do.
The likely candidates:
Avengers: Infinity War - Almost certain to have the highest opening weekend of the year. Even if we were tooking at a repeat of the Avengers to Age of Ultron percentage drop (which is arguably the worst case reasonable scenario), that's still $338M.
Jurassic World: Fallen Kingdom - I think everyone is expecting a drop from Jurassic World, but that movie did so well that even a good sized drop results in a pretty large number. A repeat of the Jurassic Park to The Lost World percentage drop still leaves you with $418M.
Deadpool 2 - Deadpool is looking to move in to the summer and play with the big boys in terms of comic franchises, and the marketing so far has been just as on point as for the first movie. The comp I'm looking at here is another record breaking R rated comedy, The Hangover. A Hangover to Hangover 2 level percentage drop still puts it at $332M.
The Incredibles 2 - The last time Pixar made a sequel to one of their more well liked movies from the early 00s, it made almost $500M. And this movie doesn't have an Illumination movie to cut off its legs. A Finding Nemo to Finding Dory percent bump puts it at $374M. Even a Monsters Inc to Monsters University percentage bump puts it pretty close at $275M.
Solo: A Star Wars Story - There's not much hype around this, and Lucasfilm is being oddly quiet in terms of marketing, but Star Wars is still the biggest brand in movies, and it's still opening on a weekend that can be really good for new releases (Memorial Day). A Phantom Menace to Attack of the Clones percentage drop from Rogue One still puts it at $372M.
Black Panther - Marvel has done pretty well at introducing new heroes recently, and this has taken Deadpool's February slot with little to compete with for weeks afterward. I think the floor here is Doctor Strange's domestic gross ($232M), with the ceiling being somewhere around Homecoming's domestic gross($334M).
The dark horses:
Mary Poppins Returns - Jumanji is looking to make over $200M with the same basic idea (a family friendly movie for around the holidays) and close to the same release frame. And Mary Poppins is a more well known brand/IP than Jumanji is.
The Grinch - It's an Illumination movie, and they've been on a good run over the past few years. Plus The Grinch is a well known character, and people might be interested in a new take on it. The biggest strike against it is that it has Wreck it Ralph 2 opening 2 weeks later to affect its legs (would you look at that, a Disney movie affecting Illumination's legs instead of the other way around).
The long shots:
Ready Player One - Spielberg is one of the greats when it comes to directing blockbusters, but the truth is that he hasn't had a movie gross more than $100M since Lincoln, and he hasn't had one gross over $200M since Crystal Skull. And let's not talk about The BFG.
Wreck it Ralph 2: Ralph Breaks the Internet - The first was generally well liked in nerd circles, but didn't do well enough that a bump up to this level is very likely. Even a Toy Story to Toy Story 2 percentage increase only puts it at $242M.
Aquaman - It has to deal with even more DCEU baggage than Wonder Woman did, with the added negative of it taking place after Justice League, so it can't just ignore everything about the movies like WW was able to by setting itself in the past. The release slot is nice, but unless the movie is absolutely fantastic, I just don't see it getting there.
Ant Man & The Wasp - The first Ant-Man was the least grossing Phase 2 movie by a decent amount, and even a First Avenger to Winter Soldier percentage bump for the sequel still only puts it at $265M.
Venom - While this is a movie based off a Marvel property, it isn't a "Marvel movie" and Sony hasn't done that well when left to its own devices for comic book movies lately. There's interesting talent in front of the camera, but the truth is that this movie is a big success if it can even get to $200M.
Dark Phoenix - The franchise is pretty clearly in decline post Days of Future Past, and even spinning this as a finale before they get merged into the MCU probably won't help it. The unrealistic best case scenario would be a First Class to DOFP percentage bump from Apocalypse, and even that only puts it at $247M.
Bumblebee - Another franchise in sharp decline, this one also has the problem of being a spinoff entry. Even if it's good, the effect on the box office probably wouldn't be seen until the Transformers movie that comes after this.
Fantastic Beasts: The Crimes of Grindelwald - This is probably the most likely of these long shots to make it, but even the mainline Harry Potter movies had a decrease between the first and second movies.
No chance:
The New Mutants - Best case scenario here is Logan's domestic run.
A Wrinkle in Time - Nothing we've seen so far suggests a breakout success. This is looking more like another Tomorrowland than another Pirates.
Pacific Rim: Uprising - First movie only made $100M domestic. This is a movie that's looking to make its major increases in other territories.
Oceans 8 - Even the biggest of Sodebergh's Ocean's movies didn't even hit $200M domestic. It doesn't even make $300M adjusted for ticket price inflation.
Mission Impossible 6 - The recent Mission Impossible movies have both ended up around $200M domestic, and I don't see this one breaking out enough to justify a huge bump from those two.
Alita: Battle Angel - Robert Rodriguez's biggest movies have only made $112M domestic, and they were both kids movies (Spy Kids 1 and 3). Even Cameron magic won't get this there.
Hotel Transylvania 3: Summer Vacation - Second movie only made $170M and the reception wasn't that great in terms of driving interest to a sequel.
Mamma Mia: Here We Go Again - Honestly, they'd better hope they don't see a Greek Wedding percentage drop.