Based on what I've seen from the trailers, it's possible that the T-Rex from Jurassic Park, the one that was attacked by Velociraptors, could be the key to defeating the D-Rex.
The reason I say this is because in the trailers, there is only one scene with the T-rex, the scene where the people are gathered around watching the T-rex eating. From the picture above, you can see that the T-rex is the same from the first movie because it is injured on the neck from its encounter with the Velociraptors.
It's possible that through movie trailer logic, that the T-rex will have a bigger role in the movie, like say save the day. By movie trailer logic I mean this:
Movie trailers will more often than not reveal more information about the movie than they would like.
Also, movie trailers could be red-herrings, in such driving your attention elsewhere, when the real plot is being hidden.
One reason for this would work perfectly into what Jurassic Park series is all about. It's about nature over emulation. It's Nature defeating human control. So it would be perfect for the T-rex to win the day, and kill the D-rex because it would nail this idea in solid. It would be the T-rex (natural) defeating the god-like created by humans, D-Rex.
It would make perfect sense that the T-Rex would be the victor in Jurassic World.
WHAT DO YOU THINK?