That is a laughably low bar, and it is unlikely for the trend you are describing to continue past the move from poor to lower middle class.
In a fair society, with equality of opportunity, it should be equally likely for a child born in a trailer park to become high income earner as it is for Bill Gate's child. That is the normal social mobility we should expect in a democratic society with no class structure. We are so laughably far off from this everywhere in the world...
And note that I completely accept that becoming a billionaire is going to be extraordinarily rare and a product of BOTH extreme luck and good work ethic. Or I would accept that, if not for the fact that being born the child of a billionaire is a guarantee to this future, or as close to a guarantee as one can ask for.