I queried Fuji directly, and received the folllowing response...

"Thank you for contacting Fujifilm, USA's Contact Center. Please allow us
to assist you.

At this time, we do not have plans to discontinue the Neopan 400
professional black and white film in the 120 format.

We sincerely hope this information has been beneficial to you. If you
should have any further questions or concerns, please do not hesitate to
contact us again. It would be our pleasure to assist you.

Thank you for your interest in Fujifilm products and services."