I think people might be getting a little too esoteric in their attempts to interpret the clues. I think we can make a reasonable assumption based on the game itself.
1. None of the previous DLC's change the world in any major way (except the premature ending in DM). LR will undoubtedly be the same.
2. Both Christine and Dog/God mention the Divide and the fight between the Courier and Ulysses. Ulysses and the Courier will be enemies.
3. We know, without any doubt, how the game ends - the Second Battle of Hoover Dam. LR will not contradict the ending of the base game in any way.
It will probably go something like this - the Courier picks up a broadcast and follows it. He'll end up in the Divide, and will either have to fight his way to Ulysses, or he'll meet Ulysses right away, Ulysses will partially explain what's going on, and he'll run off. The Courier will catch up to him, and will either have to convince him to stop what he's doing, or kill him. Whatever it is Ulysses wants to do, or attempts to do, in the Divide will fail - because we know how New Vegas ends - not with "new" America, or a G.E.C.K. transformation, or a nuclear explosion.
They might add a Dead Money style throw away ending, allowing you to help Ulysses - but that ending would also end the game.
The goal will be to stop Ulysses from doing what he wants to do.