Salamun Alaikum,
With respect, I do not concur with the interpretation of 'khalifa' to only mean 'a successor'. Depending on context, I understand it to also mean a vicegerent, an emissary, a representative and someone who has authority (Depending on context).
Please note the link with God's intention to create a 'Khalifa' on Earth and the angel’s response acknowledging the ‘corruption’ and 'bloodshed' that they would cause. Their fear, albeit dependant on insufficient wisdom, nevertheless clearly acknowledged a role of 'authority' that humankind was granted. One can only wreak havoc if one has authority. Therefore, the angels knew exactly the role mankind was going to be given (khalifa).
So the verse itself negates the interpretation of 'khalifa' as a successor in this case.
Please also note how the word 'khalifa' is also used in verse 38:26. Was Prophet David a 'successor' or a vicegerent / ruler and someone with authority?
038:026 (part)
"O David! Indeed, (We) have made you a vicegerent / ruler (Arabic: khalifatan) on earth: so judge between men in truth (and justice)..."
I hope that helps, God willing.
Joseph.