EXO, BTS, and Wanna One have been confirmed for the MBC 'Gayo Daejaejeon'.
It's most likely that we'll see all three at all three of the end-of-year music festival (two, if KBS can't hold theirs this year because of their strike), but MBC has confirmed that they will indeed be on the show.
MBC said, "This year's MBC Gayo Daejaejeon will be held under the theme of 'THE FAN', and the participants will be holding their stage for their fans. BTS, EXO, and Wanna One have confirmed their appearance."
The show will be held at the Ilsan Dream Center on December 31st.