I think (this is my speculation, not spoilage) Clint's family went poof and that's what's going to drive him to become Ronin and he'll show up and super help save the day. So it'll be the original six, just like it was in the first Avengers movie. (Someone made the suggestion MAYBE THEY WILL EACH USE A STONE, but omg, that would be so cartoony.) Probably Linda Cardinelli will go poof and we'll see Manpain, then near the end of the movie the 4400 50% will return and family hug!

....part of why I'm so salty is Marvel got me back INTO fandom. I started writing again after years and years of not writing anything. And now I'm just like "Seriously, you raptured a ton of the cast? And murdered more? What do I do with THIS?"