I have been giving this some thought myself. Any suggestions? Some mention an assassination attempt in the past, as in the comic, but what escalation ensues that compels a certain character or group to fund and create giant death robots to kill all the mutants? Magneto is defeated at the end of X-3. The cure is no longer imposed on mutants, but is something voluntary. Beast gets a promotion in the Oval Office. How can they explain or justify the Sentinel project to hunt everyone down? I am certainly not convinced that the war is over, but something must have happened to escalate these events. So what could this be? Maybe mutants like Jean are too powerful and cannot be trusted. So the government wants to kill all these powerful mutants or try to cure them. So those mutants that do not register themselves to be either cured or supervised on a daily basis need to be hunted down. Could this provoke some kind of uprising? What about the mutants that wish to conform? Or could it be genetics? Some Planet of the Apes scenario where the mutant gene breaks down and mutants become an endangered species. Or could this be an extension of the cure? The cure so radically alters the abilities of mutants that the problem can no longer be contained. Mutants become even more capricious and dangerous as a result. This could be an explanation for Rogues newly found powers. The only solution could be to kill the mutants affected by the cure, and anyone else exposed to it. But how can you stop the evolutionary process if regular Homo sapiens continue to produce mutant off spring, and now hope to exterminate them with giant Death Robots? Doesn't make sense, unless these changes were induced by the cure and all mutants affected or otherwise must be irradicated as a result?