Robert Cathles: Half Life 2 Episode 3: Prediction

Gordon and Alyx are alive in the bunker. Eli has been killed and Alyx is mourning. Dog comforts her.
Possibly Gordon can show this expression somehow too - taking off his glasses for a moment and wiping them to clear away the tears. screen going black, they wake up. But Gordon has been a lot of people die already and he wasn't fazed, so he may not react at all.

Alyx will have a newfound anger towards the Combine. Speech about the Combine not valuing life, in the same way they do with the stalkers. She's glad he didn't suffer and it was quick. She will talk about the advisors and perhaps reveal something or make a note about them.

They will obviously take the helicopter, but perhaps it isn't fueled, so Gordon and Alyx will travel back to base and meet with Magnusson and Kleiner. The vortigaunts may escort them. Gordon will have to fill up the helicopter with collected fuel, and possibly find a valve/steering wheel to attach.
It's possible it won't be safe to launch the helicopter at this base, so it will need to be transported to another base first. They may find the base has been destroyed
A map of resistance bases towards the north should point out where Gordon and Alyx may have to drop off.
Dog will stay behind and protect the base. Alyx will be tearful.

The helicopter will inevitably run out of fuel and crash, or possibly be hit by something. Possible an advisor will mentally attack them and cause them to lose focus so they crash. There will be a blizzard and they will have to travel to a base.

Possibly at Kraken base
May find footage or information here, or a layout of the area
Mossman was going to be interrogated by the Combine so we have to help her escape

There will be a heavy Combine presence. Snow uniforms or Elite Combine, Advisors, and new enemies. Possibly similar to stalkers, but adapted for the environment. There will be grey or snow hunters as well.
There will be advisors hibernating or feeding energy into the experimental technology. They will walk past an advisor doing this.
There will be elements of Aperture Science technology. Computer screens, white walls etc.

The technology "could compromise [the resistance's] work"
Risk was compromised when competing with Black Mesa which obviously caused the ship to disappear from Aperture and appear in the Arctic
It can be used against the Combine: "advantage for humanity" - "waste of potential" to destroy it or for them. There is no controlling "that kind of power"
The technology though is obviously extremely dangerous and could be used for good or for evil. So many people and large armies can be teleported anywhere in the universe immediately. We know that black hole technology is involved as a quantum tunnelling component for the Portal device.
It will clearly be portal related.

Half Life 1 was about the resonance cascade being created at Black Mesa, being held open by the Nihilanth, who was then destroyed by Gordon.
In the interim, the Combine invaded Earth in 7 hours
HL2 was about Breen escaping Earth and going to the Combine overworld. Gordon destroyed the machinery supporting it.
Episode 1 was about overloading the reactor to send a message to the Combine world for reinforcements. They did successfully send a message but it caused the reactor to explode and destroy City 17.
Episode 2 was about the remnant portal turning into a superportal to allow the Combine through. The resistance stopped it by sending a rocket with a cancelling signal.
So Episode 3 will be the Combine's final attempt to do something portal-related.

A superportal generated at the end of Portal 1 in GLaDOS' chamber and teleported her, Chell and parts of the chamber to the car park on the surface of the facility.
The Borealis was teleported sometime before the events of HL2:E2, and very likely before GLaDOS killed everyone before the start of Portal 1, with the new somehow getting to Black Mesa with an informant perhaps.
The entire Borealis and part of the dry dock was teleported to the arctic. This is somewhat similar to the behaviour of GlaDOS in Portal 1 - a big sizeable area of stuff was just teleported away.
So obviously this technology is a superportal-making device over large distances. Through the use of portals, it would allow them to avoid using the border world Xen as a relay. Or it could allow portals to be created without the need for a lot of power - just a portal device is needed.
The Combine obviously want to

Get home - just disappear from Earth and leave forever
Bring reinforcements through by opening a massive portal again
Teleport the entire Earth to the Combine Overworld (most likely and most epic! Seems likely because we know the technology is too powerful, unpredictable and takes an unexpected amount of things with it, and it doesn't act a portal exactly - unclear)

Perhaps the playing around of black holes could result in the entire earth (or sections of it) being repositioned throughout space.
Perhaps it could damage space time.
Perhaps it could allow time travel.

Something could go wrong and a chunk of Borealis and the arctic are transported to the Combine homeworld or another dimension.
The combine reinforcements reach Earth and start another invasion.
Gordon and Alyx have to escape the Combine forces, destroy the entire solar system by overloading the device / splitting up the combine, and get back to Earth
Gordon is perhaps transported to a different dimension and has to find his way back. Perhaps he travels in a tesseract and can see time.
Something has to be lost or sacrificed.
The vortigaunts will help out.
Barney could possibly come back.
The G-Man's world or home could be seen

Robert Cathles