Echt cool! Kann ich auch Französisch!
I think in the Stormcast book, it talks about Malerion spying on their training in the Gladitorium and he "watches and prepares for the inevitable day the Pantheon fails."
In Broken Realms, he and Morathi spoke, and Sigmar is SUPER pissed with her. The Stormcast were training to kill Daughters of Khaine.
I think this is also when he hints at the future.
I have no information, I'm just guessing at how lore could develop if GW follows the rules for writing of leading to the surprising, but inevitable conclusion.