Hooberus,
What if the Dinosaurs originally lived with man, and the prey/predator cycle came into being after the fall of man?
What if unicorns built space ships? This question has just about as much relationship to reality as yours.
There is absolutely no evidence that Dinosaurs co-existed with humans, or even our primate ancestors. Even if they did, predation had been going on long before the dinosaurs.
Anyway, why would god change the basic feeding behavior of thousands of species of animals just because of the fall of man? How did god do this without upsetting the balance of nature? Is there a transition in the fossil record when animals went from 100% herbivore to a mixture? (predation structures such as canine teeth, claws, etc. as well as defense structures such as shells, horns, etc.) Did viruses and parasites not exist before the fall of man? If they did, then how did they eat?
Your proposition brings up more questions than it attempts to answer.
rem