This is a fairly big deal for The Witcher Season 3. Production calendars follow a strict schedule. This slight setback can delay the release date of The Witcher Season 3 by weeks if not months. It's safe to say that Netflix will have to "delay" the still-unannounced premiere date of The Witcher Season 3, at least internally.
Netflix hasn't released a statement yet and neither has Cavill. Either way, we're wishing The Witcher star a speedy recovery with little to no complications.
Speaking of Cavill, fans were disappointed after the DCEU star was a no-show at this year's San Diego Comic-Con. Many expected the former Superman to make a surprise appearance at Warner Bros.'s Hall H panel to "confirm" that he'll reprise his superhero role in the DCEU, specifically in Black Adam. Sadly, this never happened. But, now that we know that Cavill has contracted COVID-19, it is possible that he was originally supposed to be at SDCC. Warner Bros. could have just kept quiet so as not to spoil the surprise.
We're not saying that this is indeed the case, especially after fans booed Dwayne "The Rock" Johnson at SDCC. However, Warner Bros.'s new management could be playing coy. After all, David Zaslav did confirm that he wants to see more of Superman in the DCEU.
Going back to the topic of The Witcher series. Netflix's live-action adaptation of the novel by Andrzej Sapkowski of the same name has been a huge hit. If anything, Cavill is better off dedicating his time and craft to The Witcher series as it is obviously more thought out if you compare it to the DCEU. In addition to Season 3, Netflix is expected to renew The Witcher for at least four more seasons. This is on top of the other The Witcher spin-offs in the works like The Witcher: Blood Origin.