Well, in any case this info is already known by investigators as the ATC-R/T recordings have been listened to , and frankly, unless the crew stated why they wanted to turn back, which they did not, whether it is was request or not, does not help us much .
I have heard this morning that the FDR was already looked at last night by the BEA, so if the clue is visible in tehre , e.g. , mechanical failure , loss control after turbulence , . stall ,or sudden destructive decompression , etc.. we should know pretty soon.
As stated before , it seems the CVR is badly dammaged but not unrecoverable, according the BEA it might take some " weeks"