The whole idea of gyrospheres is extremely problematic for many reasons. First and foremost, they are enclosed in the movie, something that just won't get done in a theme park. The only solution I can see to this problem is that maybe they can have it start to close and "then something goes wrong" and then it stays open throughout the ride, meaning dinosaurs can easily get out you. That could be fun but it completely goes against what happens in the movie, and Universal tries to be pretty faithful to the source material nowadays.
Even if that's the way they go, there's still the problem of capacity. These things hold two people! That means the only way to get any kind of throughput here would be to create an Omnimover type ride. That doesn't lead to a scary ride experience. They could make a bigger gyrosphere, but how much bigger could they go? Try to picture the Simpsons ride vehicle - 8 people - surrounded by a plastic sphere. That thing would be HUGE! We're talking probably 4 people, which only doubles the capacity. The more people in this thing means the sphere has to be that much larger and not only will that make it harder to climb into, it'll be extremely hard to make it look cool. The bigger you go, the less it's going to look like a sophisticated piece of hardware and the more it's just going to look like that big blow-up ball that people climb into and run around in.
Regardless, the biggest obstacle is that Universal has bigger fish to fry. There's obviously no room in USH for something like this, which means the only place for it is in Orlando. Which is currently building its Kong ride. And a hotel. And a water park. And then a Nintendo land. And maybe the Ministry of Magic. And probably Fast and Furious. And possibly a third gate. And if Nintendo Land is huge - which it will be - then they are going to fast-track Phase Two. Still, I give any Jurassic Park/World rumor a little credence simply because Nintendo, the Ministry of Magic and F&F will all go into USF, meaning IOA will need SOMETHING. If they can't find replacements for Toon Lagoon or Lost Continent, then Jurassic Park is really the only spot for a new attraction.
As for it being the "worst" of Universal's franchise films this year. Maybe, but that doesn't mean much. Furious 7 will probably be the second biggest movie of the year - after Star Wars - now that the Avengers sequel appears unable to beat it. Avengers did "worse" than Furious 7 and it is still at the $1.2B mark. It's still projected to be one of the highest-grossing movies of the year, with its only competition being Minions, the two Pixar films, James Bond, Katniss Everdeen and Ant-Man, all of which could hit a billion but probably won't. Jurassic World would have to get horrible reviews AND negative word-of-mouth to not reach a billion. So even if Minions ends up beating it, that certainly doesn't mean it won't be seen as a success.