The downside is that $10,000 may only be enough to buy a stick of gum in 2033.
In other words, if in 2033 a stick of gum is $10000, which implies there was high inflation between 2023 and 2033, which likely means Fed increased rates even more, wouldn't that cause your rate of return to go above 5% and therefore roughly maintain the value of your assets (assuming Fed keeps interest rates above inflation)?