I've posted this in another thread, and really didn't want this one to be too River centric. This also isn't exactly a theory, more what I think would be a satisfying and romantic ending 
1) Young River/ Melody is conditioned to kill the Doctor from birth by Kovarian et al.
2) They also put in a fail safe that means she'll die if she fails.
3) They rescue her and she's raised by Rory and Amy instead (either from birth or from spacesuitgirl age), then when she meets the Doctor and instead of killing him she falls in love.
4) Because she failed, she'd have to die, but to save her, she has to kill the Doctor on the beach, and by interrupting his regeneration, it saves her (partly Time Lord) life.
5) This means that the Doctor would die at his 'first' meeting with River, just as she died for him at his first meeting with her.
6) The big suprise I'd like at the end of the series (not a surprise if guessed, I know)? That the Doctor ISN'T saved at the end, and we begin the next series with the companions having to work alone.
and either
7) Young River had her memory wiped in order to prevent him ever finding out beforehand and orchestrating a rescue.
or
8) It's someone else who shoots the Doctor (maybe Amy), again for the overall purpose to save River's future.
Even if River in SITL has met other Doctors- 'time can be rewritten'- so by killing the present Doctor, he becomes the only one she'll ever meet in her future. This also fits in with the fact that Doc 1103 seems to have filled in the rest of the diary before he goes to die.
Though of course this is unlikely because they'd have a Doctor-less Christmas special.
1) Young River/ Melody is conditioned to kill the Doctor from birth by Kovarian et al.
2) They also put in a fail safe that means she'll die if she fails.
3) They rescue her and she's raised by Rory and Amy instead (either from birth or from spacesuitgirl age), then when she meets the Doctor and instead of killing him she falls in love.
4) Because she failed, she'd have to die, but to save her, she has to kill the Doctor on the beach, and by interrupting his regeneration, it saves her (partly Time Lord) life.
5) This means that the Doctor would die at his 'first' meeting with River, just as she died for him at his first meeting with her.
6) The big suprise I'd like at the end of the series (not a surprise if guessed, I know)? That the Doctor ISN'T saved at the end, and we begin the next series with the companions having to work alone.
and either
7) Young River had her memory wiped in order to prevent him ever finding out beforehand and orchestrating a rescue.
or
8) It's someone else who shoots the Doctor (maybe Amy), again for the overall purpose to save River's future.
Even if River in SITL has met other Doctors- 'time can be rewritten'- so by killing the present Doctor, he becomes the only one she'll ever meet in her future. This also fits in with the fact that Doc 1103 seems to have filled in the rest of the diary before he goes to die.
Though of course this is unlikely because they'd have a Doctor-less Christmas special.
