WMG / The Elder Scrolls Online

The Breton nightblade was not raised as a zombie he was undead from the beginning
Notice in the first trailer how he seems to carelessly send the orc soldiers and just to check on the defenders response and then without a hint of disappointment goes into being a badass after the soldiers fall onto the chasm. Well here's my take on it he didn't care because they were all empowered by Breton magic remember this are the guys who brought you hagravens and forsworn in Skyrim I wouldn't be surprised of they were all liches from the beginning

TES Online does not take place in Tamriel
It takes place in Coldharbour, which has already been said to be a cruel mirror of the real Tamriel, your characters and others just think they're in Dawn's Beauty rather than Molag Bal's Arena. It handily explains the oddities with the set-up, explains away the problems with the handwave justification for being able to come back and is perfectly in the Corruptor's perview.
  • this appears to be jossed with the Coldharbour reveal video
  • Jossed.

The third cinematic trailer is going to be the Nord's show.
During the last two cinematics there has been a segment where the sound aside from the music drops out and the focus character in question displays some truly awe inspiring combat feats that ends the serious fighting for that trailer. The first cinematic had the Breton McNinja single-handedly demolish an imperial garrison while the second had the Altmer spellsword obliterate some armored Dremora and destroy Molag Bal's chain gate unassisted. The third is going to feature the Nord trucking through a horde of undead like a superheated buzzsaw through paper mache and end with the zombie Breton getting beheaded.
  • This is actually fairly accurate. The release trailer, "Siege", depicts the Ebonheart Pact laying siege to the Imperial city. While the Nord doesn't do much in the way of fighting, we see how clever he is. The Nord uses the Aldmeri woman he pulled out of the rubble earlier in order to rip a hole through the Imperial City wall, ending with a one-on-one confrontation with Zombie Breton.

The Bigger good is going to be The Ebonarm
Or at least there will be a reference to him, Sai or the Citadel.

The plot is another in-universe book
Putting together a coherent timeline of Tamriel is already difficult, thanks to the flexible standards of scholarship found in the books scattered through the games. If this game proves unpopular or is rife with continuity issues, Bethesda will simply declare it to be an in-universe work and therefore of debatable historical truth.

Lord Harkon will appear
He's a devout worshiper of Molag Bal and an immortal vampire. The timeline is also right for Serana to make a cameo, assuming the guess of her imprisonment being second era is correct.

If the game looks like it's going to fail, Zenimax will introduce Tiber Septim himself
It would be a good way to draw more interest and possibly save the game. And if it doesn't work, they can instead end the game with Septim taking over.
  • He doesn't show up until roughly the end of the Second Era, though.
    • A little more detail on why this won't happen: ESO takes place in 2E 582 on the Elder Scrolls timeline. The birth of Hjalti Early-Beard AKA General Talos/Tiber Septim does not take place until 2E 830. It's possible that they COULD put Tiber in the game via some sort of future vision from the Scrolls. However short of a massive retcon or time travel any type of long term appearance of Tiber is highly unlikely.

Sheogorath will have a prominent role or at least more than a token appearance
Three reasons. First, with Molag Bal having a prominent role, more of the Princes are bound to be included; Second, he's pretty much the Ensemble Darkhorse of said Daedric Princes; and Third,cheese!
  • Confirmed. Sheogorath is the Big Bad of the Mages Guild questline.

Boethiah and Mehrunes Dagon will be prominent Enemy Mine allies of the player characters.
Boethiah hates Molag, and Dagon's driving motivation is the destruction of Nirn- he's not going to stand by and let Molag do it.

At some point, Molag Bal, the King of Rape, will hum Singing In The Rain
He IS voiced by Alex DeLarge.
  • Jossed.

Elder Scrolls Online is historical fiction
This explains the entire interrugnum as well as the improbabilities of the factions themselves, as well as various other factors. The entire game is historical fiction written by an author in Tamriel!