Let's do my local So Cal parks. These are reasonably realistic, but are not necessarily what I really think will happen.
Disneyland Resort (parks only):
2017: Disneyland Railroad reopens, Rivers of America reopen, Fantasmic returns, All elements of Season of the Force leave Tomorrowland except Star Wars Launch Bay, Launch Bay is expanded to cover two levels with models of Star Wars Land, Guardians of the Galaxy retheme of Twilight Zone Tower of Terror
2018: Upgrade remaining Fantasyland Dark Rides (Mr. Toad, Snow White, and Pinocchio), Monsters, Inc. and the surrounding part of Hollywood Land closes, Fantasyland Theater demolished
2019: Star Wars Land begins AP previews after holiday period and opens to all visitors to correspond with Episode IX's release, Star Wars Launch Bay closes
2020: 65th anniversary celebration, with the debut of a new fireworks show and new version of World of Color. Additionally, an Arendelle mini-land opens on the site of the Fantasyland Theater with a Frozen trackless dark ride, meet and greet area, and a full service restaurant. All of Hollywood Land, with the exception of Guardians of the Galaxy Tower of Terror, closes.
2021: DCA's 20th anniversary, highlighted by the opening of Marvel Land. The land, which takes over Hollywood Land and backstage area, features a copy of the Iron Man Experience, a Captain America roller coaster similar to Tron Lightcycles Power Run, an Infinity War show in the Hyperion Theater, a Big Hero 6 show replacing Disney Junior, an Ant-Man dark ride replacing Monsters Inc, a new restaurant in the Muppet Theater, a Marvel Museum/Meet and Greet in the Animation Building, and a flat ride themed to Hulk. Additionally, DCA changes it's name once again to "Disney's Cinematic Adventure" and modifies the remaining California sections to fit this new theme.
2022: Star Tours is relocated to Star Wars Land. Toontown closes. DCA adds a new family attraction where Maliboomer once stood.
2023: Prep work throughout the park begins for the 70th anniversary. Mickey's Soundsational Parade is replaced by a new daytime parade.
2024: Much of Tomorrowland is closed for a major overhaul. Goofy's Sky School is replaced by a new family attraction.
2025: Disneyland's 70th anniversary. A completely overhauled Tomorrowland opens, with a new version of the PeopleMover, the return of the Rocket Jets, a Wall-E dark ride in Star Tours's former space, and a new unique attraction in the Tomorrowland Expo Center building. Additionally, the world of Zootopia opens on the former site of Toontown, featuring two family-friendly rides (one a dark ride) and various shops, restaurants, and meet and greet opportunities.
Universal Studios Hollywood:
2017: Secret Life of Pets dark ride opens on the Lower Lot. Shrek 4-D closes.
2018: Jurassic World attraction replaces Revenge of the Mummy. Studio Tour loading area is relocated to Lower Lot. Waterworld closes.
2019: Jimmy Fallon ride replaces Shrek 4-D. Retheme existing portions of Lower Lot to a uniform theme.
2020: Wizarding World of Harry Potter expansion on Lower Lot, with an area themed to the Fantastic Beasts trilogy.
2021: Nintendo Land replaces Waterworld and the former Studio Tour loading area, with two separate mini-lands connected by a warp pipe.
Knott's Berry Farm:
2017: Knott's Soak City expansion with two new slide towers containing 7 slides (1 family raft slide, 2 innertube slides, and 4 trapdoor body slides). Boomerang closes.
2018: Gerstlauer Infinity Coaster on the former site of Boomerang and Riptide. The coaster is slightly smaller than Monster (100-125 ft tall, ~2200 ft long, 3-4 inversions) and similar in intensity to Silver Bullet.
2019: Fiesta Village refresh with a new flat on Windseeker's site.
2020: Remove Pony Express and relocate backstage buildings from behind Bigfoot Rapids.
2021: B&M Hyper. The station is roughly in the same location as Pony Express's, with the lift climbing over Bigfoot Rapids and the majority of the coaster taking place in the cleared area behind the ride. The coaster is approximately the same size as Mako (200 ft tall, 4,700 ft long).
Six Flags Magic Mountain:
2017: Justice League dark ride on site of Action Theater.
2018: Mack PowerSplash on Flashback's site. The ride is accessible from both Magic Mountain and Hurricane Harbor. Additionally, SFMM begins selling combo tickets with a gate at this access point to allow easier two park access. Additionally, Viper receives two new Vekoma trains.
2019: Cyclone Bay refurbishment with a complete GCI retrack of Apocalypse and a couple new flat rides. Apocalypse receives a new name to fit the new theme.
2020: Samurai Summit overhaul. Superman switches to running one train forward and one backward, Ninja receives two new trains, the Sky Tower is reopened, a new restaurant is installed in the Laughing Dragon building, and a year-round Willoughby's Mansion maze is added. Additionally, a chairlift is installed running from Spin Out's spot to the base of the Sky Tower.
2021: SFMM's 50th anniversary, featuring a RMC T-Rex Giga Coaster (placement TBD).
Coaster Count: 535 (114 wood, 444 steel); Park Count: 110
Top 5 Wood: El Toro, Voyage, Thunderhead, Outlaw Run, Boulder Dash
Top 5 Steel: Superman the Ride, Fury 325, Millennium Force, X2, Intimidator 305