Hello,
For the latest version of PhotoScan Pro I suggest to use the following script (saved as .py file and executed from Run Script dialog):
import PhotoScan
chunk = PhotoScan.app.document.chunk
suffix = "tiff"
for camera in chunk.cameras:
camera.label = ".".join([camera.label.rsplit(".",1)[0], suffix])
camera.photo.path = ".".join([camera.photo.path.rsplit(".",1)[0], suffix])
this script swaps the extension for the cameras from the existing to "tiff", but you can change it in the script body to any other.