There appears to have been prior discussion here: Recording API doesn’t report transcription status (ZOOM-126066)
@tommy Might you happen to have any updates around this feature? 
We’d like to be able to check in the API if a Cloud Recording will have a transcription in the future, but doesn’t yet. In my testing, it appears that the transcript is not included in recording_files if it’s transcribing and not completed. (Actually, including this in the recording.completed webhook event would be great too, or instead!)