It's going to be almost impossible to find a worthy villain to take over Thanos' role in the MCU as the "TOP BAD GUY". But in the meantime, we will also need a "secondary top villain" to take over the potential place of Loki; and that's where Norman Osborn could come into scene. There has been a lot of rumors about a potential Post-Credits' scene of "Spider-Man: Far from Home" that seems to indicate Norman Osborn is the one who bought the Avengers' Tower and he's gathering the Sinister Six. Of course, I deal this information with a grain of salt; but in case this would be true, this could lead us to the MCU's adaptation of one of the greatest and possibly more polemic arcs in the Marvel Universe: Dark Reign.

Let's suppose for a minute that the rumored information is true. Well, based on that, Norman Osobrn could be aiming to usurp Stark's role in the world; both as a business man and as "hero". To do that, I guess he could start by forming HAMMER, as both SHIELD and Hydra were supposed to be destroyed in MCU, so Norman could pick up the pieces to form HAMMER, just like he did in the comics.

1º) Having buying the Avengers' Tower, Osborn would want to form his own "wannabe" Avengers to look like a good guy in public. This could actually be a combination of both, Norman Osborn's Dark Avengers and Baron Zemo's Thunderbolts. It's difficult for me thinking about enemies outside of Spider-Man's rogue gallery for this team, but I have some interesting candidates:
- "Superior Iron Man": Just like he did in the comics, Norman Osborn would usurp Tony Stark's identity as Iron Man. However, considering the identity of Iron Patriot was already used, I believe there's another candidate to cover this place. And that is "Superior Iron Man". Since this suit was created as a "pseudo-symbiote", it suits perfectly for Spider-Man to fight; not to mention this could give us something similar to the Black Suit's arc while avoiding Venom's connection.
- "U.S. Agent": A parody of Captain America would be needed, but I'm not sure who could be the guy to cover this place. On one hand, I believe Norman's variation of the Super-Soldier's serum could lead us to the creation of the Goblin Serum.
- "Ragnarok": The artificial clone of Thor could be Norman's version of Thor, but I suspect this could lead us to a popular villain of Spider-Man. In case it doesn't appear on "Far from Home" with the other "Elementals", maybe this guy could became Electro.
- "Grey Hulk": Which character could become Norman Osborn's version of Hulk? Well, if we follow the origin based on Gamma radiantion, there's one candidate, the Rhino.
- "Trick Shot": A criminal archer could suit the role of Hawkeye, probably Buck Chisholm to avoid direct connection with Clint Barton's brother, Barney. However, there's another archer who could take this role in Spider-Man's gallery of foes, Kraven the Hunter.
- "Black Cat": Sounds weird, but this character could work as Osborn's Black Widow. However, if they are loyal to the comics, Felicia could end up having a crush on Spidey and desert from Osborn's side.

All these characters could end up becoming their alternative selves as an incarnation of the Sinister Six, once Spider-Man defeat and unmask them in public; but we all know how tricky Osborn can be, even if he's not crazy because of the Goblin's serum. So, to control both sides of the board and have a team to do the dirty work. That would be the first incarnation of the Sinister Six, before Norman and his Dark Avengers take their real roles. Let's see:
- Vulture: He's a good candidate, but considering that he's like an honorable villain here, it's hard to believe he will follow Osborn without questioning. This could lead us to Blackie Drago, the second Vulture; who could be more willing to kill Spider-Man.
- Scorpion: He's definitely a potential candidate.
- Shocker: A more advance version of this bad guy, looking like the comics version, is possible.
- Chameleon: If rumors of his debut are right, he's another candidate. However, considering his talents are not necesarrily fitten for combat, he could actually have a different role.
- Mysterio: We don't know how this guy will end up in the movie, but if it turns out his classic self, then Spidey will have a real problem; especially since this guy knows his secret identity. (I mean, they are both unmasked in the trailers).
- Hobgoblin: If Norman debuts, then the legacy of the Green Goblin can't be far away. However, I believe his role as the Green Goblin could be "postponed" to his final battle against Spider-Man; and in the meantiem, we could get another goblin.
- Doc Ock: If the Sinister 6 debut, its original leader should appear sooner or later, although I don't know how he will do it.
- The Prowler: Aaron Davis made his debut, so he could become the Prowler in the future. I just hope he will become an honorable villain like the Vulture.

Well, what do you think of this theory?