Some reports have suggested that the lack of any R/T call following the last routine message is an indication of a very short time interval between what went wrong and impact.
While this is obviously possible, in my experience there is another possible reason for the silence - the crew were too busy trying to sort things out and had not given up on recovering from whatever had gone wrong.
Whenever I have lost control due to a mistake on my part or an issue with the aeroplane I have always got on with doing everything I could to recover the situation first before climbing on the R/T.
Off-hand I can only remember one example of a crew saying they were going to crash ("We are falling") and that was when their tail had detached in the cruise at height. Not much you can do about that hence the R/T call.