I know, it's still a bit early to think about the new sequel to Half life, but it's never too early to have fun.

Dicuss all things you think will happen in the future. If you know something or ANYTHING of the sort about the game, don't share it. We want to be pleasantly surprised.

Here's what I see in the game:

Alyx and Gordon are flying over the snowy tundra, heading on the right track to the Borealis. Suddenly, their helicopter gets shot down by a new combine device, and they go down.
When Gordon and Alyx come to, DOG is broken and busted. Alyx sobs for a moment, then decides that she is going to fix it, telling Gordon once again, "I'll stay here and take care of DOG, while you go find out what shot us down."
On your way to the Borealis, you encounter a new combine enemy, a snow snake. Kind of like Lost Planet, this thing is made out of white metal, with laser-guided missiles. You defeat it, but it lands on you, knocking you unconsious.
When you come to, you find yourself being dragged through a make-shift camp in the snow. they lock you in a jail, soon following Alyx. She said she was mid-way fixing DOG when a combine sentry knocked her out. Suddenly, she pulled out her unlocker thingy, she uses the laser to cut the metal. Once you're free of the cell, she hands you a new weapon, a metal pipe broken off from the toilet. This shall be your new crowbar for the time being.
You fight through hordes of combine, surprised at how badly they want you to stay here. You break out, and head south towards the Borealis.
Once you arrive at the ship, Alyx marvels at the sight. Once you get inside, there are boxes of whatever (I have no imagination for the Borealis contents, so bear with me). Alyx hands you the makeshift charges that Kleiner gave her before they departed. You plant the charges, and get out of the ship. Soon, you find yourself staring at five dozen combine, with a grin-wearing breen standing in front of you.
He tells you that you almost killed him, before combine sentries found him and carried him away, healing most of his fractured/dismembered body. He lifts his sleeve and two pant legs to reveal a robotic appendage now replaces his flesh and bone.
Alyx and gordon struggle as they are hed captive once again by the combine, forced to watch as the combine defuse the charges and carry out the crates. Suddenly, a half-rebuilt DOG comes to the rescue and barrels down the combine, showing impressive stuff as he kills everybody. He then lands on top of Breen, and hesitates to kill him as he begs for his life. Suddenly, Breen pulls out a gun and starts firing into DOG's head, cutting off it's circuitry etc.
Alyx goes into a slow-motion cutscene, taking Gordon's crowbar and whacking Breen in the head so hard, it almost seemed like it was gonna fly off.
Soon alyx cries and starts frantically trying to rebuild DOG, bu it was no use. She gathers up most of dog and put inside a Combine backpack, not before taking a coat as well. So now, you both get to see a sexy Alyx in an eskimo suit, and a naked combine.

I'm a bit too tired to finish the rest, I was just writing down what I was thinking.

Oh, a while later she shall rebuild DOG in a smaller "puppy" form, starting from scratch once again.