Did Writers Know When It Jumped The Shark?

Rating: 6/10 (21 March 2009)

This film started out with a real grabber. The whole time capsule thing was working as was the predictions and it had me riveted waiting to find out what was going to happen next.
Then everything went left and the movie bounded over the shark as Cage begins a wild chase to tell everyone about the end of the world.
I absolutely believe this screenplay wasn't written with the ending that was in the movie. I figure around one third of the way through someone said, "hey this is way too M. Night Shymalan, better beef up the special effects!" That's when the explosions started.
Then another Hollywood big-wig said, "hey, we need to add some extraterrestrials or this will never hit" and so enter the blond guys in the woods. These scenes look like they were re-shot after the fact.
Finally as Cage is on his knees waving to his son on the space ship, I expected the credits to roll, but no. I feel pretty sure a focus group was show the first cut and they said it was a downer, so...after a rewrite and lots of money on special effects. Voila! End of the world.
Ten, after another focus group, comes the two kids in Eden ending that looked completely out of place and I feel pretty sure was tacked on after audience reactions ranged from"but what about the kids?" to "that's a downer".
All in all, the whole thing went way off the rails and squandered any viewer interest in favor of bad theology and worse writing.
If anyone can confirm my theories of rewrites and re-shoots, please let me know. Otherwise, I have to believe the producers just got lost somewhere along the way to what promised to be a good film.