"Well then. You must shoot me."
They just had to go and ruin it, didn't they? The Doctor has organised the first official meeting between the lizards and the humans, the participants are slowly working out how they can fit it all together, and then the lizard commander busts in ready to start shooting. At the same time the party upstairs Tazer their hostage to death. Idiots, the lot of 'em.
I did like the reference back to the fixed points in time - we first saw that with Waters of Mars, where the death of the main character was a fixed point of the universe. The Doctor makes a big thing of how this isn't one of those fixed points, and so making it work is entirely up to them.
There's something seriously screwy going on with the canon in this series - given that they don't think humanity is ready for the lizard race, that implies that most if not all of the alien visitations from the past few series haven't happened. The hospital badge with the wrong date is looking more and more like a production goof (especially as the date when all this mess started is shown in-universe to be the 26th - the date of the final episode), so it's not just that the date has been moved round. Here's a random theory: if the Tardis really does explode (which looks likely, based on the shrapnel), then the explosion undoes everything that the Doctor has achieved with the Tardis. He gets eaten from existence by the cracks, and so do all his actions.
Speaking of the cracks, they're definitely getting more menacing, and interacting more with the universe. They seem rather picky too - it ate Rory out of existence, but ignored the Doctor when he stuck his hand in. Interesting piece of shrapnel - the strong implication is that the Tardis exploded. I guessed something similar in a comment elsewhere, though my theory was more a "travelling through time leaves holes behind" than "Tardis fall down go boom". Interestingly they've already referenced/foreshadowed blowing up the Tardis in Amy's Choice
One last thought - what happened to the ring? Rory very carefully put it in a special holder thing in the Tardis, and it's still there. So what's in it? Is it going to trigger a sort-of Bad Wolf moment in Amy?