Every single one of us on this forum right now are millionaires. The amount of Bitcoins we own right now is worth millions by 2140. The truth is that none of us would be able to spend the money on goods and services since 2140 is outside our life expectancy.
By 2140, none of us will be alive to witness the event of the last halving and for those that will probably make it till then which I strongly doubt, they would be praying to be better off dead than alive because the existence in the world will be like hell to them and they will wish they’re not still alive by then. Even if they have a lot of bitcoin saved till then, they can’t enjoy it again as enjoyment comes with an healthy and strong body and soul for it.
Thinking that the amount of bitcoin everyone holds now will be a very huge value in the future just reflects how optimistic bitcoin holders are and also praying for a better future for bitcoin to be at its peak after every four years and continue to win globally as an acceptable and tradable currency of exchange.