I get enough Heechul on Knowing Brothers personally. I find him at times to be too overbearing, he takes the spotlight away, as if all the attention has to be on him. So I'll be happy with just having it back to the way it was before tbh.
EDIT: It's been confirmed by Weekly Idol staff now:
He will film the episode in late September and it will air on October 5.
Hani (EXID) and Heechul (Super Junior) will leave the show.
For the past 6 months, they have filled in for Hyung-don's absence.
Currently, there are no plans for Hyung-don to return to Infinite Challenge.