Something tells me he's going to be perfectly content to settle for richest man on Earth.
Anyone motivated by money would have stopped working that hard many, many Billions ago.
I'm sure he's motivated by other stuff too but he's very clearly also motivated by wealth accumulation to some degree.
I would argue that many of the billionaire class (outside of wall street) are more interested in their projects and goals than strictly capital accumulation. Especially those who have signed off on donating a majority of their wealth after their death.