I'm going to post this here in the spoiler thread just in case.

Has anyone considered the possibility that a third party has gained control of the galaxy in the power vacuum left by the weakened Empire and the small rebellion? In the leaked images, the old Rebel bases are being used once again. This would make no sense if the Empire was still battling the rebellion, but if it was an entirely new threat, the Imperial remnant could have made an alliance with the rebellion, making these bases useful again.