While 4chan, in terms of reports for movie news, is very often complete and total garbage that should never be trusted, when it comes to video games it actually can be fairly reliable. Among the recent slew of leaks from the video game section of the board were details about Fallout 76 and some of the newly announced Pokemon games, so there may very well be a grain of truth to this reported news about Square Enix and Marvel's upcoming Avengers title.
Cutting to the short of it: "The Avengers Project" is Avengers: Ultimate Alliance. But it's not just Ultimate Alliance 3, it's a full reboot with the name on it (think something like the new God of War, minus the story continuity: similar name, totally new gameplay/story structure). That's the reason why the tagline of the first teaser was "Reassemble", to hint at it being a reboot. This is also why the previous Ultimate Alliance games got uprezed recently for current-gen.
The game takes place from the perspective of multiple Avengers after a cataclysmic incident broke the team apart (think more Dissassembled than Civil War), but there are 3 which are the core focus: Captain America, Iron Man, and Scarlet Witch (who you heard in the trailer). They aren't the ONLY playable characters, but they are the leads of the story. Gameplay wise think a mix between Uncharted and Infamous
It'll also have connections putting it in both the same world as the PS4 Spider-Man game (that Sanctum Sanctorum appearance in still images was not just for fun), as well as Eidos Montreal's Guardians of the Galaxy. Marvel Games wants in on that shared universe idea that have made the films literal billions of dollars.
Peace
Now, there is some grains of truth sewn into this (which could be either adding to the veracity of the report or just someone being clever). There are connections from Spider-Man PS4 to other Marvel characters like Doctor Strange, and Eurogamer and Kotaku both separately reported that Deus Es was being put on a backburner for Eidos Montreal to develop a Guardians game (which statemetns from Eidos have backed up, with them officially saying they are working on an untitled game).
Either way, with the game almost certainly showing up at Square Enix's June 11th presentation, we will know soon enough about what this Avengers game is (as well as their purported Guardians of the Galaxy game).