Considering it's source material, which is very much like a coaster. I have a feeling it will be similar to Space Mountain or Rock and Roller Coaster, just with a higher level of theming. Since the FJ is so story based, I have a feeling this will be less so, especially if Daniel Radcliffe is not involved with shooting more scenes. I think the premise will be something like "take a tour of the bank vault" and the ride will be very dark, with only a few video screens.
Like I said earlier...Universal Studios actually has more "all ages" rides then Islands...so antoher thrill ride would actually balance out just fine. It's Islands that needs more young kid friendly stuff..because all they really have is Camp Jurassic and Seuss Land. Also, as mentioned The Hogwarts Express will probably be pretty tame, although you'll need a multi park pass just to experience it.
Is it possible that Universal may just raise ticket prices, and completely do away with the one park pass? It would save a lot of confusion on guests that want to ride the Express. It will be interesting to see how they handle this issue.