Thanks for reaching out about this—These updates are still ongoing, and you will continue to see the “page_number” field returned in our API responses in the meantime (and during the overlap period of ~6 months). To keep up to date on this ongoing enhancement, you can follow our Changelog page where this will be documented once fully implemented.
We will also send an official notice once all Batch List APIs have been updated to support next_page_token (at which time the six month adoption window will begin).