Owls, foxes and coyotes gain an advantage if they can spot their prey from far off and plan their attacks. It takes more than pure speed to catch a jack rabbit. Well, perhaps for a while. Natural selection would begin to work on the rabbit population and those that turned white too early, or stayed white too late in the spring would be subject to greater pressure from predators. Soon the timing of the coat changes would be shifted to reflect the new average dates of snow cover and snow melt.
Nature can adapt to change, even if it's human induced changes to the environment.
Sorry, I haven't found any good links yet.