I would love to see Ironheart make a billion (hell, I'd be ecstatic just to have an Ironheart movie as long as it wasn't terrible), but something like that would be guaranteed to take a serious hit from the sense of her 'replacing' RDJ. It's a nice thought that her being the first black female star might make up for that, but I honestly doubt it. (Not that I'm saying the movie would bomb, it's just not likely 1b straight out of the gate material.) And no mcu solo is getting anywhere near 2 billion anytime soon, certainly not on their first outing. The only solo superhero who's ever managed that much was Batman, the most famous hero in existence, at the literal climax of his most popular series ever. Maybe Black Panther 3 could do it, if the series popularity keeps growing. Otherwise, it probably won't happen until ticket inflation makes the 2b mark a lot less imposing.