When pandoras actor called ainz dad in what I believe is ep 11 of ISEKAI QUARTET that was a refrence to the light novel which happens to be one of the upcoming ones in the anime this could mean some sort of announcement soon.
I figured this event of Isekai Quartet suggests it happen right after Overlord Light Novel Volume 10. Pandora's Actor doesn't call Ainz his "father" until Vol.10 after all.
I believe they will announce it at the anime expo next week
It is only what I believe thoe not guaranteed
What do you think?