Auf der Homepage der AOPA steht auch was dazu:

"Although the approved engines comprise a large percentage of the GA fleet—used mostly in aircraft that burn lower octane fuels—the remaining 30 percent of engines require 100-octane fuel and account for 80 percent of total avgas utilization, he said.

Those engines should make up the bulk of the “fleetwide expansion” of approvals to use unleaded fuel that George Braly, GAMI’s chief engineer, told an AOPA webinar audience in September that he was expecting from the FAA early in 2022. At that time Braly’s upbeat presentation described the FAA’s attention to the issue using terms similar to those tapped by Millner—noting that the approval process was by agency standards, “progress at the speed of light.”"

Also soll "early in 2022" eine erhebliche Erweiterung der Zulassung kommen. Mal abwarten.