Since we speak about a new JP movie,I'd like to write a few of my thoughts about its might be scenario.,and how it's too hard to make one without breaking the already established canon.
I mean,we had two islands with dinosaurs,Isla Nublar and Isla Sorna,and after the events of the first JP movie in Isla Nublar,this island gets bombarded by Costa Rica air force,with dinosaurs, buildings and stuff getting killed/destroyed. At the end of the third movie it is shown that the US Navy and Marines storm the second island,and it is assumed that they've gone there to do somewhat like what the Costa Rica government did at Isla Nublar: Kill and Destroy.
So right now in the universe of JP, inGen is a broke company because its investors took their capital away from it after two failed tries of making a park which both ended only in casualties and lawsuits,and the only two dinosaur islands that existed got treated by militaries. There shouldn't be anything alive in any of these islands to see,and if there was something alive,probably the islands are surrounded by military forces that wouldn't allow people to go there.
Where would the fourth movie take place ? If they just unveiled in it that there is yet another secret inGen island,a 3rd Isla,it would just be too stretched out and rehashed for anyone to like this plot. But if they made a movie in one of the two islands we have already seen in the movies,it would be like ignoring the plot of past movies,like they didn't happened,which would be a negative factor for the enjoyment of this film too.
Of course in the second book we get to know that some dinosaurs managed to somehow travel the distance from the islands all the way to the shore of the mainland of Costa Rica without getting drowned,which have lead to many weird sightings by the people,that the government rejects as hoaxes. But if they tried to make a sequel out of this and make a movie based on Mainland,it would be nothing like the JP we know and love. You know,JP works because our heroes are trapped in a deserted island,far away from the security and comforts of civilization,which creates this feeling of despair. If the movie was taking place in a city full of people,it wouldn't be the same. It would be bad.
I guess the only option that stays that would make a fourth movie to not break the canon and already established lore/story is a far fetched scenario where the US military instead of going to Isla Sorna just to destroy the dinosaurs,captivate some of them and takes them to a remote top secret US military base,to train them for future use as weaponry. But again, how would our known characters get involved in a top secret military project ?
Hmm...
If a fourth movie ever comes out,I'm curious to see what will be the plot they thought.