I suppose it's always dangerous (and daft) to speculate on these things before the AAIB has published its findings, but if it was due to natural causes (or indeed a mechanical/carb icing problem) it does look at though it was at least a reasonably controlled initial descent to the ground. If he messed up a forced landing in the last few seconds, that really would be a terrible shame.
Hopefully, the AAIB will find the cause fairly quickly...