In fairness, a delay of a week or so would seem to be in order—McCarthy dropping out does change things. Other people might run. Even if others don’t, people who were planning on voting for McCarthy finding out at the last minute that they he is not an option and having to vote between one of the two remaining candidates would be placed in an unfair situation.
Tell that to the people when some congressman or senator drops out of a race at the last minute! Elections have consequences!