I love the Pratt, but if I have any concerns (based on the trailers, video released so far) it is that his character will be just a bit too much of a comedian. When I think back to the original Jurassic Park, and even The Lost World, the characters had some funny lines, but they weren't delivered in an overly comical or hokey way. The overall tone still took everything quite seriously, and I just hope Pratt doesn't play Star Lord in this movie. I love the guy, but I think there is a need for seriousness in a movie where dinosaurs goes on a rampage and eats people.
I'm fine with Pratt being a funny dude in the first part as long as he doesn't run around doing overly silly one-liners during the chaos. That line from the first trailer, "Depends on what kind of dinosaur they cooked up in that lab" sounds like something Horatio Caine would say before putting on his glasses. Let's not have a whole second half filled with those type of lines.