If every human in a few decades lives a life with as much comfort, health, security, etc. as today’s billionaires, does it matter that the centatrillionaires of 2066 are off building private space habitats in the asteroid belt or trading ultra-rare crystals mined from Saturn’s rings or whatever?
If I want to influence policy I need to get a lot of like minded people via grassroots means to have enough say to get my direct elected representatives to consider a policy. If the billionaire class wants to influence policy they will talk about it with elected officials over golf.
Worst case scenario the wealthy can spend money to gain foreign citizenship and move. Your average citizen is mostly stuck with whatever government and laws exist in their current country.