A lavish funeral, cameo appearances, maybe even a Force Ghost Apollo if the situation calls for it.
It could even happen post-Rocky’s death, which might be ideal considering Sly announcing he’s done playing the character.
Should that script ever come, then Viktor is the obvious choice for the opponent.
His backstory is already laid out, so a writer wouldn’t be bogged down with establishing a new opponent and could dedicate the rest of the time to Adonis grieving and mourning.