Aint It Cool appear to have clarified some earlier reports regarding The Simpsons Movie.
Apparently, there will be no dome over Springfield - though Frink does suggest it, and that is probably where the story started. The power plant accident that Homer causes leads to the water becoming polluted (Again? Will Blinky return?) and, therefore, the majority of townfolk move away. Erin Brockovich's role will be as herself, so that part of the movie seems to virtually write itself.
One of my mysterious sources tried spinning me a line about Apu going back to India as part of the plot, and while that seems like a reasonable assumption, they couldn't substantiate it - so I report it only as a reasonable assumption.
Even less credible are the rumours that Michael Jackson will be reprising his infamous role. I'd like to think its true, but I don't. Not yet, anyway.
Any more Simpson Movie info, send it my way.