Jurassic Park/World

Short answer: Move along to fish, birds and mammals

Already, the series has done the inexplicable-- they have run out of dinosaurs. With dozens of famous species to use, they already had to start making up "new" ones. They have already moved on to insects. 

After six movies, the dinosaur idea may have run its course anyway. They might do an at-sea movie with water-dwelling dinos. But what are those next to ocean liners, ocean-going barges, or modern battleships and subs? We used to kill whales from mere sailing ships.

The next steps in evolution are still available, though.

There are several species of giant, flightless birds that are taller than people. What if someone got the idea to clone them, for their meat, eggs, feathers, and even bones. "If a chicken can feed 3-4 people and one ostrich egg can feed 8 people, why not raise giant birds and feed whole communities? And if they are flightless, they will not be able to spread and take over, the way the flying locusts did."

Unfortunately, many such birds are predatory, and none are domesticated. So we have at least one movie in which the world is threatened by giant, flightless, formerly extinct birds. 

And then a zoo gets the idea of resurrecting extinct mammals. If they can "zoo" an elephant and a tiger, why not a mammoth and a saber-tooth cat? How much harder can it be? Care would have to be taken, however, to not confuse the film with the Ice Age movies, so as not to have children prepare for watching one of those, but seeing a very realistic saber-tooth cat.

And in the last one, early forms of human are being resurrected through cloning as a medical measure by a doctor fearing the endless cycle of pandemics, and wanting to make the human immune system more "more robust." 

In short, the series that made us believe that dinos could be real now must make them extinct again.

Dragonheart

Short answer: More diverse dragon voices

The Dragonheart story runs through five movies, and I am sure there plot holes have formed that need to be sewn up... but let's face it. There is really only one reason anyone watches a movie with a dragon it it:

The dragon.

Some great performers have voiced dragons, from John Hurt in the Merlin series to Benedict Cumberbatch in the Tolkien movies. 

The Dragonheart series began with a Sean Connery-voiced dragon, and has since given us Robby Benson (who also voiced Disney's "the Beast"), Ben Kingsley, Patrick Stewart-- all white guys... and (finally) one woman, Helena Bonham Carter.

But everyone knows that some of the best dragon-type voices belong to Black actors-- James Earl Jones (now 91 years old) and Morgan Freeman immediately spring to mind. Avery Brooks, who played Sisko in Star Trek: Deep Space Nine, can also rumble menacingly when asked.

Dragons also have Asian versions, so maybe we could use George Takei (Star Trek's Sulu, who's 85). Or Michelle Yeoh. 

Just because the stories are set in the British Isles does not mean the dragon speaks with a British accent. So sure, you could use Christopher Lee (who's 93) or Jeremy Irons or Ian McKellen (83).

But this is the 21st century, so we are used to (and even prefer) to mix it up a bit.

Plus dragons can be thousands of years old. Why would they have a British accent, necessarily? They may have been around since before English even sounded like English. 

I'm giving the ages of some of these actors because if the producers want to use them... well, not to be rude, but they should hurry.

Transformers

Short Answer: 1) the 1800s and/or 2) "Voltron" the McGuffins 3)Monsterverse crossover

The Transformers movies seem to want to also be National Treasure/Da Vinci Code movies, rewriting actual human history to attribute events to the Transformers and their foes. 

But they kind of start that... and drop it. There is stuff about Camelot, and stuff about WWII. And... that's it. Still, having this idea gives us the possibility of genre crossovers, like the sci-fi/fantasy and sci-fi/ war movies so far. But there is a whole lot of history left to look at.

So, let's look. I recently learned that for part of the 1800s, the following four cultures co-existed in different parts of the world-- The Wild West (US), The Victorian Era (England), The Samurai era (Japan), and the tail end of the Pirate era (Caribbean). 

Which means we can have one or more of these genre crossovers. We're talking Transformers and/or cowboys and/or samurai and/or pirates and/or steampunk. How much fun would the CGI staff with steampunk Transformers? That turn into steam locomotives, steamboats, airships...

Plus, Charles Darwin, Sherlock Holmes, Dr. Jekyll...

...or Ebenezer Scrooge. Yup-- we could have A TRANSFORMERS CHRISTMAS, with TIME-TRAVELING ROBOT GHOSTS. If you think that could be cool...

And of course, still plenty of (violent) history left to shove Transformers into: The Revolutionary War, for example. Ancient Rome or Egypt. Napoleon's Europe. (Just rifle through the Drunk History or Epic Rap Battles of History playlists. History's Greatest Hits are pretty readily available.)

Another running feature of the Transformers series is high-tech McGuffins-- objects whose having (or preventing from having) drives the plot. These include the All Spark, the Talisman, the Space Bridge and Quintessa's staff.

But what if we borrowed a page from another classic robot animation-- Voltron. The gimmick there was to combine huge robots into a gigantic one. Now that I think of it, this is also done with the Infinity Gauntlet in the MCU.  

So... do that with the Transformers McGuffins. Join them into one giant MegaMcGuffin! What happens when they all join together. Whatever that whatsis is, is going to be pretty powerful, and everyone is going to want it.

Another option is to have the Dinobots fight MechaGodzilla, and so bring Godzilla, King Kong, and the rest into the Transformers-verse. Yes, Pacific Rim did this, but that was mechs (with people inside) fighting kaiju. Self-driving robots fighting kaiju might be different enough to work.