So is the whole game unwinable seeing how there are no more live space/time players?
Dave, Jade, Aradia, and Kanaya are all still alive.
Dave, Jade, Aradia, and Kanaya are all still alive.
Retcon is short for Retroactive Continuity. This is the process of changing facts that were already stated. John is going back and changing parts of the story that were told years ago. And the changes that he is having an effect on how the story will continue to be told, such as Vriska still being alive.