Today I got this email response from
NCSCFollowup.NSC@uscis.dhs.gov:
Good afternoon,
USCIS records indicate that the Service is waiting for VISA availability.
Please note that if an applicant wishes to transfer their pending I-485 application to their 2nd preference approved I-140 petition, a request for conversion must be made in writing, but a visa must be available to transfer.
If you have already submitted a written transfer request, your request will be kept in the file. The transfer can take place once visas are available.
The National Customer Service Center’s toll free number is 1 800 375 5283 or you may access the CIS web site at
www.uscis.gov should you have any further questions or need additional information.
Regards,
USCIS Nebraska Service Center
EX0357