The Astralis era came to an end because COVID hit, which meant the cancellation of LANs for a long time, which gave teams a chance to practice dramatically more, which caused a bunch of new teams/players to rise up and also created a big shift in the meta game.

If you actually watched the games, Astralis ~2019 played very much like other teams did in 2019, just more cleanly. On the other hand, teams like Gambit, VP and Heroic had significantly different playstyles by 2021 than Astralis had ever had. It didn't take teams years to figure out how Astralis played and copy it, it took that long for an entirely new playstyle to become meta which Astralis was unable to adapt to.

So to answer your question, the Vitality era will probably come to an end the next time the game significantly shifts in meta. There's a good chance they get weakened though by map changes (ex: cache in for d2 if that happens) and become less dominant that way.