I don't see it happening, but anything is possible at this point. Any privilege which can be conferred by a piece of paper can be rescinded by another piece of paper (except for gun-nut rights, it seems...).

It'll be messy if they try, however. We ARE backsliding in this quagmire of a society but I seriously doubt we're going step so far back that black people will resign themselves to less than second class again.