In order to stop the doctor dying does anyone think that Matt Smith's regeneration story will be River killing him to make him regenerate thereby avoiding the murder at the lake.

This way River's murder is not necessarily a bad thing but a necessary sacrifice

Obviously this would involve the long game from the writing team, but does anyone elese think that this could be possible?

You've set me thinking, but at a tangent.

What if his death by the lake is to avoid a future regeneration or to pay for future crimes.

My suspicion is that the doctor bifurcates at some time and the astronaut is the doctor himself correcting that situation.

Moffat has said very, very clearly that it is the doctor and he is dead.

If he is a bifurcated doctor then that can remain true whilst leaving the franchise intact.