If you were looking forward to recruiting Peter Parker to join The Avengers, you might be out of luck, as the Spider-Man DLC, the first to be released to the game, will apparently be exclusive to PlayStation 4.
This feels apt given Sony's love for the Spider-Man font in it's PlayStation logos, but in any case, the deal likely has something to do with Sony's rights over the Spider-Man character. Sony Pictures, the motion-picture arm of the company, license the rights of the character to Marvel for use in their movies, and as such, have likely used this leverage to garner the exclusive.
Crystal Dynamics confirmed that the character will be PS4 exclusive, and will be releasing in early 2021 as a free update to the game.
We can’t wait for you to add Spider-Man to your Marvel’s Avengers roster in early 2021, and as we’ve promised before, he will be available at no additional cost to owners of the base game, exclusively on PlayStation.
Other characters will also be added to the game as free updates down the road, and hopefully not exclusively to any one particular platform. There's clearly some licensing issues tied up with Sony and Spider-Man, but this isn't a great start to the game's character road-map...