Key things that happened:

Dead Guardian is sent into the central battery as some sort of a ritual.
GLs are on the hunt for terrorists that attacked them in previous issue.
GLC is accepted to the United Planets and due to that Guardians are changing how the corps work. From my understanding sectors that overlap with UP's activities are removed and those lanterns are assigned to new tasks.
Crux worlds are explained, basically 7 core planets that are driving the progress in every universe. Krypton and Xanshi were Crux worlds. Earth is another Crux world, other 4 were not named.
Earth being Crux world is offered as an explanation for why it has so many super powered beings and ties into some Morrison's stuff by mentioning that it will eventually become fifth world replacing New Gods. Hal Jordan is assigned to protect Earth and is now only Lantern operating there.
John is set to lead 1000, yes 1000, Green Lanterns to some dark sectors that are hidden from Guardians by some multiversal mumbo jumbo.
But before any of this can happen central battery explodes. Issue ends with Jo arriving and her ring saying that there are no GLs left on the planet. We see Simon on the ground and Teen Lantern still has her powers because gauntlet works differently and technically she is not a lantern.

In other words some eggs are being broken here. I feel like this is either going to be one of the better GL runs or complete disaster that everyone will try to forget few years later.