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

Context:

If a practice is obsolete, it may be in the process of being replaced.

Please provide 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!

Maybe obsoleting or obsolescent (as @Robusto suggests) is what you're looking for?

Usage notes:

To obsolete is often used in computing and other technical fields to indicate an effort to remove or replace something.