However, if you all remember "Rebirth" when Hal is describing the way the GLS with him use the ring. It is Guy who has the most will power and how he is always leaking energy. My thought is that his control of Will and his own short temper may be the catalyst to bring the Red Lanterns back to a normal state of mind. However as I've been saying, I have a horrible yet good feeling that we are losing at least one of the Earth GLs in a truly heroic way and each one has had that moment save Guy. So I think we may see Guy lead the Red Lanterns, after taking power from Atrocicus and have a "Battle of the Light Brigade Moment" against the black battery. Cause if the Red Lanterns can go into "Berserker Mode" the thought of their loved ones with a black ring would only power them more.
As for the loss to the corps, I think we'll see Mogo die. It's been hinted that Salik ordered all the rings back to Mogo to wait and that Mogo is prophesied to die. Along with the fact Sodom is supposed to be the last GL in the future on a dead mogo with countless powerless rings. So either Mogo or Oa (And the corps being forced to move to Mogo for their counter attack) are going to be destroyed. This would be important for the Corps either way.