Now that I think about it, what kind of an ending what that be for the Craig era? Bond kills Blofeld with his bare hands and is presumed KIA by his superiors after he suffers amnesia escaping from the Castle of Death. Then in the PTS for Bond 26, he shows up and attempts to assassinate M....
From certain point of view that would be very interesting. But than again, we've seen something like that in recent films. M was killed in Skyfall, nearly died in TWINE and QoS. Bond presumed dead in SF.
That plot was intriguing in Fleming novels because it was fresh, unexpected.
I'm not sure if it'd work with movies at this point. Not yet at least. In my humble opinion, of course.
And let's not forget that in The Man With The Golden Gun novel Bond was brainwashed by Soviet Union. There is no such adversary to Great Britain at the moment. Who would have the motivation (and means!) to execute this plan? Assuming we don't want to see another ex-agent trying to kill the chief of SIS.