Taxonomy Switcher – WordPress Plugin
This plugin allows you to select your “From”, and “To” Taxonomies, to convert all terms. Optionally select a parent term to limit terms to switch. Typing term names will do a live search of terms with the name you are typing AND possess child terms.
Earlier today, I needed to switch a bunch of terms from one custom taxonomy to another. This plugin saved me a bunch of time, so I thought it was worth a bookmark for future reference.