What we don't know
The P2F or not question has been answered at least twice in the negative in this thread.
But one question I haven't seen dealt with is what is the significance of the instant loss of contact at operating height - if that is what the reports mean. If the aircraft stalled, would the transponder continue to signal in descent for a couple of minutes? Isn't that what AF447 did? If that happened, how would it be recorded? If so, when is it likely to be made public. if it didn't, could it mean the aircraft broke up at operating altitude?