Just saw that everyone's favorite blogger Devin Faraci said that there are NOT too many characters in this movie, and that it all works. Though he did say that it might feel a little "retro" after Age of Ultron.
Look, I'm no fan of Devin, but I think that if a guy who can't go five minutes without making fun of the title or taking a shot at DC/WB is saying that the movie works and that it's not overstuffed (AND that it's truly a MOS sequel... he said this a little while ago) then I think we can put to rest any fears that the film is going to be a crowded mess. Now, granted, a lot of things can change as a movie moves from the script to the screen, but it sounds like this movie is really going to work.