When will Vex be on the PBE?

At the beginning of the year, League of Legends and Riot Games announced The Ruined King Viego was coming to the game. With his announcement, they also revealed that the next three champions to come in 2021 would all revolved around him. The first one was Gwen, The Hallow Seemstress with Akshan coming next. Although the Vex was supposed to come first, they moved her back. Now the question becomes, what is the Vex PBE release date?