A single word for "in the process of being replaced"

Preempt has one definition meaning to take the place of; displace

Then there are also these synonyms:

supersede: 1. To take the place of; replace.
2. To cause to be set aside, especially to displace as inferior or antiquated.

supplant: To displace and substitute for (another); this term seems to be replacement through scheming or force

The noun forms would be preemption, supersedure, and supplantation.

The second definition of supersedure is interesting. From Merriam Webster: 1. The act or process of superseding.
2. Replacement of a queen bee that has grown old or weak by one that is younger or more vigorous.

I learned something new!

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