As for the DMCA, usually not since most FOSS licenses are explicitly irrevocable, but with the WTFPL, who knows.
That's almost the same thing. Like if someone dropped their domain name and you grabbed it up. The customer / user isn't going to notice a difference but it's now being represented by someone else.
I don't think anyone cares enough to really do anything about this though. Mostly curious if it was possible to do something about it but I'm guessing the waters are pretty untested.