Not sure if resolved this for batch relinking to files that are the same but with different extensions,
for example moving from .MTS straight from camera ingest to let say .MOV @ 422HQ.
There are a few ways.. but this is by far the quickest.
1. Export XML for FCP from Premiere.
2. Open XML in text edit or alike.
3. Find and replace all .mts -> .mov
4. Save XML.
5. Import XML to Premiere.
6. Relink and edit.
This is a project wide shift to different extensions for your media. If you want change just for one sequence, then you will have to save those sequences out separately.
WORD.