All of those actors have played coy about whether or not their characters will actually be brought back to life, but it’s basically a given that most, if not all of the dusted heroes will be brought back, namely because folks like Spider-Man and Black Panther have sequels on the way.
It likely involves all the characters who were dusted at the end of Avengers: Infinity War.
Once you throw them into the equation, such a huge gathering is possible, though that doesn’t make it any less cool to see on the big screen.