A Miami friend of mine has alerted me to this article in the Miami Herald of 31 August.
(If, like me, you don't subscribe to the Herald and ad blockers make it even harder to read, try opening the link on your mobile. I was able to play an audio version of it on mine).
Anyway, the gist of it is that Miami Beach is in discussions with the Duke of Richmond to host a Goodwood Festival of Speed in the spring of 2024, on South Beach's Ocean Drive. Several Miami people, including Mayor Dan Gelber, are quoted, though there is no comment from Goodwood.
My friend expressed surprise that the article mentioned the hill-climb - she says hills are in short supply on Miami Beach.
I hope, if it comes off, that US aficionados will continue to come over to Sussex for the real thing!