These rumors are now debunked as AMD told the press that Zen 3 remains on track for a 2020 launch. An AMD spokesperson said that "the rumor on Zen 3 delay is inaccurate."
The call was chaired by AMD's client-segment product managers who were speaking purely in context of their product segment, which is how we deduce that they were referring to "Vermeer" and not [just] "Milan." They were responding to speculation that "Zen 3" has been delayed to 2021, forcing AMD to refresh its existing IP.An exact launch date for the Ryzen 4000 desktop processors is unknown. It's believed to be late 2020.