In his video, Cavill calls his appearance in Black Adam "a very small taste of what's to come." The caption also speaks of a "dawn of hope renewed" and that people's patience will be rewarded.
Despite years of rumors that Cavill was no longer going to play Superman (which continued to circulate as recently as this summer), there hasn't actually been any official announcement that he's turned down the role. However, since he starred in Mission: Impossible: Fallout and The Witcher series, we've seen Superman appear less and less in the DC Extended Universe movies. Before Black Adam, the character's last appearance was a few seconds of footage in Shazam! of 2019.
It will likely be a while before Cavill's Superman returns to theaters, as Man of Steel 2 is still very early in development, with no director or writers. He may appear in some DC movies in 2023, but for now, fans can only hope that Cavill wears the Superman cape again.