Nope, you are thinking about that entirely wrongly.
It is not that everyone has so much money that it becomes worthless through deflation--
It is that nobody has any to spend, but still have outstanding needs. It becomes about as useful a commodity to facilitate trade as refined uranium is. Which is to say, not at all, because nobody except a very few have any refined uranium. The same will be true for money.
Instead of money, people will trade something else. Fuck, it could be damn bottle caps for all I know. Just not money as investors consider it.
To be useful in the process of securing goods or services, ordinary people need to have that commodity to trade. This is not devaluation due to deflation, it is devaluation due to lack of liquidity in the market.