There are people who paid thousands to tens-of-thousands of dollars for a promise that their car would eventually have "full self driving".
A not-insignificant portion of those people have lost any chance at actually getting FSD, whether by their car being totaled in an accident, or having sold it, or such, without ever seeing working FSD.
As far as I know there's no way to get a refund, and people very obviously didn't get "full self driving" as advertised by Elon, so it really does seem like some people paid for a promise that turned out to be nothing... which sounds like lawsuit material to me.
There have also been multiple public promises that FSD would be delivered in a matter of years (like in 2016, the promise that "by the end of next year, FSD will take you across the country safely while you sleep").
If anyone bought FSD due to believing those promised timelines, that also seems like it would be a pretty strong case for a refund to me.