We can also put away the silly argument that Solo's poor performance was purely the result of fans boycotting the movie over The Last Jedi, and that the fact that it was released up against Avengers: Infinity War and Deadpool 2 had absolutely nothing to do with it.
Considering what Disney did in the ROS to try to retcon TLJ, as well as the few jabs thrown Rian Johnson's way, my guess is Disney knows that fan backlash had quite a bit to do with it. Not the sole reason, but was definitely a big part of it.
I doubt it will break the billion globally, if it does it will be very slightly.
That would definitely be a big underperformance. Especially since this film probably cost over $300M to make with all of the reshoots. Add in a crazy marketing budget and this film may need ~$900M to break even.