X-Men: Everything You Need To Know Before Marvel's Big Relaunch
9. Cable Is Young Now
Speaking of last year's Extinction, that book also saw Cable lose a few years.
This happened as the younger version of Cable went to the future and saw a timeline that was not supposed to occur - one in which all of the X-Men were dead. This Cable then came to the present and determined that the cause of this new timeline was the fact that the aforementioned younger original X-Men were not in the correct time, so he went about kidnapping them with the goal of returning them to where they should be.
When he attempted to take Ice Man, the older Cable tried to stop him, to which young Cable responded by 'retiring' (killing) his older self - hence leaving the young Cable as the only Cable.