I'm not sure if anything has happened yet, but I suppose his tweet is in reference to the possibility of the Supreme Court revisiting their initial ruling regarding mail in ballot extension deadline.
"An opinion accompanying the Supreme Courts order by Justice Samuel Alito, joined by Justices Clarence Thomas and Neil Gorsuch, suggested that the court may still revisit the case after the election and toss out contested mail-in ballots. Although the Supreme Court declined to rule on the matter before the election, Alito wrote that there was a "strong likelihood that the State Supreme Court decision violates the Federal Constitution." Pennsylvania plans to segregate ballots received after Election Day in case the court takes future legal action to challenge them, CNN reported."
