Phoenix will be the killer in the last case.

And you WON'T see it coming.

He'll turn out to be the killer for every case since the first AA game.

Motive: Fame.

D: The satisfaction players have gotten from winning every case up until GS5's last case will have been for naught. And it will be Apollo's job to bring him down. Just like his daddy mentor, Kristoph.

Oshi---

The new prosecutor, Cody Hackins from 1-2, will fall in love for a more grown up Pearl Fey and continuously bend to her every will. One of the cases which will relate to the final case somehow will consist of Godot and Iris some time in the 7 year gap, after both Godot and Iris are released from prison for murder in self-defense and accessory to murder in self-defense charges as the Defense and the defense's aide. Payne will not be the prosecutor in 5-1, but the defendant who, after an apologizing profusely about his behavior in the prior cases vs. Appolo, Phoenix, and Mia, is found innocent and promises not to be so harsh on Apollo anymore, even offering to help Apollo as an assistant on one or two cases, though he will end up being pretty much useless. The game will have major roles filled by Spark Brushel and Lamiroir/Thalassa. Interestingly, Spark was gathering info for Zak Gramarye's biography in 4-1 and 4-4, so he knows everything that Zak would know himself about anything concerning his life. Thalassa, having regained her memory, will choose to "watch" Apollo from afar, not revealing her real name nor her otherwise unknown relationship with Apollo and Trucy. Apollo's father is still among the deceased, but is brought back on only one occasion by Pearl Fey. The case that Godot will be a defense attorney for will be the cold case of the murder of Apollo and Trucy's father. Franziska and Edgeworth will make cameo appearances from time to time, but not be really important, just kinda like Phoenix in 4-2. Adrian will be the owner of Lordly Tailor and, while requesting Phoenix's assistance, ends up with Apollo.

Ema will share the detective spotlight on at least one occasion with Gumshoe or the newly reinstated detectives Neil Marshall and Angel Starr. And for Oos-chan, I added a part in my theory where Richard Wellington was a witness to a crime that happened within the prison walls and is delivered tea by the bellboy (who now owns the Gatewater), who also delivers tea to Atmey. Both Wellington and Atmey look rather worn down for being in prison for over seven years. Wellington has circles around his eyes from lack of sleep and his blonde lock of hair was cut off by a random inmate while Luke has been reduced to using a makeshift magnifying glass monacle using a toothbrush, some dry macaroni, and another inmate's contact lens. There will also be cameos from other famous villains from the Phoenix Wright series that haven't already been executed such as Redd White, who had so much dirt on everyone, he managed to secure a life sentence over execution, Damon Gant, whose work as the Chief of Police granted him some standing in court and also got a life sentence instead of execution, Matt Engarde, whose power with the network allowed him to serve life in prison while only being released to shoot episodes of Nickel Samurai as it got much more popular after the murder trial, and Furio Tigre, who got help from Bruto Cadaverinni after being pestered by Viola to help Tigre get a lesser sentence. Bruto used his power to make sure Furio got Life rather than execution. Finally, the quick-fire lists:

Married at the beginning of GS5:

-Ron and Dessie (still going strong after eight years)
-Gumshoe and Maggey (It was inevitable. How could Maggey turn Gumshoe down?)

Dating at the beginning of GS5:

-Larry and someone related to a GS5 case.
-Iris and someone related to a GS5 case.
-Adrian and someone related to a GS5 case.
-Neil Marshall and Angel Starr OR Lana Skye (After 1-5, they got a lot closer and, if they haven't already married, they're going to!)
-Viola Cadaverinni and Furio Tigre (Even after the incident, Viola visits Tigre on rather unorthodox dates in the detention center.)

Dead at the beginning of GS5 (if not dead already):
-Manfred von Karma (Executed)
-Dahlia Hawthorne (Executed)
-Turner Grey (Murdered by Ini Miney in 2-2)
-Kristoph Gavin (Executed)
-Frank Sahwitt (Executed)

Married by the end of GS5 (excluding those already married):
-Phoenix and Lamiroir/Thalassa OR Iris (Either works)
-Neil Marshall and Angel Starr OR Lana Skye (The same one he was dating at the time.)
-Viola and Furio (Again, very unorthodox)

Dating by the end of GS5
-Apollo and Ema (Bound to happen eventually, but not with Klavier. He's too uch of a free spirit to even consider dating, especially Ema. At least, not until GS6.
-Trucy and Wocky (Trucy loves Wocky's pies, Wocky loves Trucy's magic act! Match made in magical pie heaven!)
-Phoenix and Thalassa OR Iris (if they don't get married)
-Cody Hackins and Pearl

Those alone after all 5 games (until GS6):
-Godot (refuses to take on another companion after Mia's passing).
-Richard Wellington, Luke Atmey, Damon Gant, Redd White, Matt Engarde (Sorry, Oos-chan, but knowing that GS5 will never feature homosexual relations with those who don't follow a certain stereotype a la Armstrong (pardon the pun), these gentlemen will be alone for a long, long time.

Anyway, that's all of it.

I take it that when you say Neil Marshall, H de K, you really mean JAKE Marshall, right? Because Neil's dead (since Gant killed him two years before 1-5).

Apollo himself will be a killer, but will effectively hide it until the very end when he's set to "defend" the "murderer." It'll turn out that Apollo is really a genius and acts somewhat stupid to get people to like him.

The one to figure it out will be Trucy, but nobody will see it coming.

And then, Trucy mysteriously disappears....

At the end, when Phoenix mentions taking the Bar Exam, I thought he may become an attorney again. He will probably be killed later like they did to Mia in AA. I kid. But in all serious nature, I believe that Phoenix will become a lawyer again to put matters to rest while Apollo is somehow inactive.

What I want to see is an older Maya or Pearls. I seriously want to see what they can still contribute to the story at their ages during the new GS. If anything, I'd like Larry to come back to annoy us again. But not Moe. If I have to see Moe again, I swear I am eating my DS and making sure GS5 goes straight to hell.

It turns out that even Thalassa doesn't know who Apollo's father is, because he was conceived during a fivesome with Marvin Grossberg, Damon Gant, Manfred Von Karma and the Judge.

Apollo then claws his own eyes out because of the horrible mental images of his conception.