First, changing an object's WF revision in Prod is bad practice. It leads to other questions of data and other types of integrity.
If you study the WF% tables, you will find that some are "structural", some are "transactional" and some are both. The transactional records track the state and history of each object as it goes (and has gone) through workflow.
Moving an object to a new revision of a workflow could be as simple as changing the revision on a couple transactional records (e.g. WFASSIGNMENT, WFCALLSTACK), but it could also be more involved. In theory, WF revisions mean the WF process changed, and the nodes and actions by which your object got to its current assignment or wait node, for example, may not exist anymore, or there may be more of them. In moving an object between revisions, your data may now say that something happened that cannot possibly have happened. Or you may miss a spot and that may prevent the object from completing its WF journey or may prevent you making more revisions.
It may be an inconvenience to get your object back to the "same" place in WF, but I can't see any Pros to changing its WF revision. I just see a lot of risk and questions of integrity. I say don't do it.