It's not a "guess" - it's expert opinion based in current trends and projections of what those indicate is most likely for the future. Sure, it could be wrong, but there's absolutely no reason, given the state of the world, and most marginalized people's daily experience with inequity to believe that it is. Honestly, the "best case scenario" is some sort of catastrophic event that forces humans to stick together and do better.

Your white guy optimism comes off as kind of dismissive of what the rest of us are dealing with on the regular.