It appears Apple has been further reducing its current iMac offerings by removing two storage configurations from the purchase options. While this could indicate an upcoming unveiling of an iMac range featuring M-series Apple Silicon, the continuing worldwide chip shortage could force further hardware delays.
https://www.notebookcheck.net/Latest-iMac-discontinuations-could-point-to-impending-announcement-of-Apple-Silicon-M-series-iMac-models-but-chip-shortages-may-cause-more-hardware-delays.528763.0.html