Ok so after reading Glasslands and Primordium, I believe I know what will be the backstory to Halo 4.
Scroll down for updated theory
In Primordium it says that the UNSC has ONI scientists stationed at the Ark. This means that ONI must have reopened the portal on Earth. The flood on the Ark was destroyed during Installation-04B’s premature explosion (lol.) While damaged, the Ark still supports gravity. ONI scientists have found the terminals that John found and learned of the Librarian, the Didact, and anything else the terminals talk about. While there they find a duplicate of 343 Guilty Spark. This duplicate was made of himself while he was on the Ark (either during Halo 3 or during the Flood-Forerunner war.)
When the Portal closed at the end of H3, it just sent the Forward Unto Dawn several lightyears away from the Ark. Once Cortana’s beacon was activated, it took over 5 years or more to get to the scientists stationed on the Ark. This lets them know that Master Chief is still alive. They contact Earth via the Portal, Earth sends the UNSC Infinity that contains a Mark VII suit. The ship goes through the Portal to the Ark. With the Forerunner slipspace drive on the Infinity, the captain jumps to the signals location, which takes possibly a couple weeks or days.
Here’s a few possibilities on how the Infinity finds John at the Shield World. They mind find the ship exploding from the strain of the Shield World’s tractor beam. They manage to get John out and treat his injuries and such on the Infinity, and fit him with the Mark VII. Then the ONI agents on the ship send units into the Shield World, knowing that Forerunner technology could be useful.
Or they arrive and John is already in the Shield World and send in troops to recover him, and give him the Mark VII once they find him.
Spartan-IVs are on the Infinity so we’ll definitely see them. Also it’s most likely that we’ll see Fred, Kelly and Linda. During a 4-player Co-Op, players will paly as these 4 main Spartan-IIs. The host is obviously John with everybody else being Fred, Kelly and Linda. Naomi may or may not make an appearance.
Also the Mark VII has very unique abilities such as transforming the energy shield for multiple purposes, such as energy daggers and walls. Possible new gameplay elements or armor abilities?
Updated Theory
In Primordium it says that the UNSC has ONI scientists stationed at the Ark. This means that ONI must have reopened the portal on Earth. The flood on the Ark was destroyed during Installation-04B’s premature firing.
While damaged, the Ark still supports gravity. ONI scientists have found the terminals that John found and learned of the Librarian, the Didact, and anything else the terminals talk about. While there they find a duplicate of 343 Guilty Spark. This duplicate was made of himself while he was on the Ark (either during Halo 3 or during the Flood-Forerunner war.)
When the Portal closed at the end of H3, it just sent the Dawn to two different places. One piece to Earth, the other towards the Shield World. We see in Origins (which is being told by a Rampant Cortana) that the Ark’s Portal can teleport several objects to different locations. It is possible that Mendicant Bias send Chief towards the Shield World. The Shield World may be close to the edge of the galaxy due to the nebula seen at the end of Halo 3. Though it could also be “near” the Ark.
The reason for the Shield World’s location outside of the galaxy is a simple one. When Mendicant Bias began serving the Precursor, he gave away the locations of all the Shield Worlds. So the Didact had a Shield World moved to outside of the galaxy (along with others.) This way the Flood wouldn’t find it within their reaches.
In Winter 2556-Spring 2557 Cortana’s beacon is picked up by ONI scientists stationed at the Ark. The UNSC Infinity, also at the Ark, uses it’s Forerunner slipspace drives to go to the Shield World. Though they could just use a Portal that the Ark can create to go to it, but I doubt that. It’s also possible that if the Shield World is near the edge of the galaxy, that the Infinity just goes to it from whatever planet it was stationed at.
Fred, Kelly and Linda are all stationed on the Infinity to train S-IVs. Or they could be on another ship which goes to the Ark (or from a planet to the Shield World as stated above) and then follows the Infinity to the Shield World. Knowing that John is using “obsolete” armor, the UNSC brings along Mark VII, which Kelly, Fred and Linda may have.
When the Infinity and possibly other ships arrive at the beacons location they stumble upon the Shield World. They rescue the Chief before the ship explodes. They give him a pair of Mark VII armor and give him, along with the other S-IIs and S-IVs (possibly even S-IIIs), to go into the Shield World to recover any Forerunner technology. Now Chief may already be in the Shield World by the time that the UNSC shows up, and then they go in and rescue him.
As for Cortana, we’ll have to wait and see. I can’t find anything that suggests that she’ll live or die or what. So I’m pretty much leaving her out of the theory. Each paragraph has the potential to be wrong or have a variation of it. I feel that this is the most likely theory for the first couple of levels of Halo 4.
Four Player Co-Op will have the host be John, and the other players be Fred, Kelly and Linda. It would be interesting to see if 343i makes to where players can pick who to play as instead of being set with.
I made a video of the simplified version of my theory in case this is too confusing for some. Link
Variants
There are several ways my theory could go that I have thought up. It could be possible that the Ark plays no role in the game. The UNSC Infinity could just make a slipspace jump to the Shield World.
