What would you call a person who is being replaced by another

In my specific case, I need a single word to call an employee who is being replaced by another due to his/her retirement, death, resignation etc.

Anything like “Replacee” may be suitable.

Solution 1:

One word is Incumbent

adjective

1. holding an indicated position, role, office, etc., currently:

the incumbent officers of the club.

...

noun

4. the holder of an office:

The incumbent was challenged by a fusion candidate.

Source: Dictionary.com

This word implies that the person being referred to is the current holder of the office or position, but might not hold it in the future.

Solution 2:

Predecessor

A predecessor is exactly what you describe. A person whom was replaced by another.

Barack Obama's predecessor is George Bush Jr.

This word isn't exactly thrown around in everyday speech either. It's usually reserved for higher up positions (like my presidential example). That doesn't mean it couldn't be used for other jobs though.

Jim Jones is the predecessor to the fry cook at Wendy's

meaning Jim Jones was the fry cook and has since been replaced.

The person who replaced Jim Jones is called the successor, more particularly Jim Jones' successor.