Cue jokes: "We're all sedevacantists now."

How funny. But no, "we're" not. Sedevacantism is predicated not just on a vacant see, but the Church's teaching on the papacy and her own constitution.

Many who are chortling about how "we're sedevacantists now" will accept whoever's elected—even Pope Susan:

https://www.wmreview.org/p/susanvacantism