can also be used to mean "later" or "at a later time". For example, if someone says "I'll see you bye and bye", it means that they will see you later, but they don't specify exactly when.
In some cases, "bye and bye" can also be used to mean "eventually" or "in the future". For example, if someone says "I'll get around to it bye and bye", it means that they will do it eventually, but they don't have a specific timeline in mind.