I have contacted both Darton, Longman, and Todd (DLT), and Penguin Random House (the parent company of Image Catholic Books, who will be the US publisher of the Revised New Jerusalem Bible). So far, I have received no response from DLT, but Penguin Random House promptly sent the following response:
We do not have access to why the book was delayed.
I am showing a tentative release date now as Aug 2020.
It is possible that the date could change again in the future, but I would not be able to say for sure at this time.
We apologize for the inconvenience and you could certainly follow up in the upcoming months for updates on this titles release date.Penguin Random House Customer Service
It sounds like the delay for more than a year is correct. When I first heard of it, I wondered if August 2020 was simply a placeholder date while they ironed out whatever production or approval issues they’re facing. With this response, it’s looking more likely that we won’t see an RNJB until at least August of 2020.