Jurassic Park 4 is a doomed concept, I'm certain of that. It has all the traits of films that bombed and sucked. They don't have an inspired idea for a story, but they want another film. This kind of motivation has never resulted in a good film.
I wish I could disagree with you, but you have the history of forced movie sequels backing you up.
Aside from that, I am not a fan of movie series that take breaks of a decade or more between installments. Yes, I eagerly awaited the Star Wars prequels, and then Indy Jones 4, but those served to illustrate a sad truth: When you come back to make a new installment after so much time, it just doesn't feel the same. The best sequels come out between one and five years after the previous film (and naturally flow from the story of the previous one rather than trying to copy it).