Planet Scar could just be a side-effect of the Lifestream being depleted during the battle against Meteor. Life diminishes when the Lifestream is taken away, as shown by the barren wasteland surrounding Midgar and the damaged, monstrous animals which increased when Mako became widespread. But that's probably a discussion for another thread, since this one is dedicated to jubilation at the news of AC finally getting a release date after years of dithering.