EN World published a story April 23 with news of upcoming products that are set to feature the infamous death knight (https://www.enworld.org/threads/lord-soth-appears-to-be-a-darklord-again-in-ravenloft-the-horrors-within.718852/).
You might remember that Sithicus was the name of the realm in Ravenloft that Lord Soth ruled over. The new Actual Play series has a Dungeon Masters campaign called “Ashes of the Black Rose” where the players must escape Sithicus. The first episodes can be watched here: https://www.youtube.com/watch?v=mY9w7n84PmM&list=PLfS8QgUdeGYqr4_6btWrlIz9A45UtJ5iY . This uses content from the book ‘Ravenloft: The Horrors Within’ which is due to be released on June 16. A pre-order bonus available for that is the mini-adventure ‘D&D Encounters: Shadows of Sithicus’.
Not everyone is a fan of Lord Soth ever existing in Ravenloft, but now it seems the mists have dragged him back again.