Not much i guess
Assuming Singer and co. are still on board and the sequel comes out in 2009 , i think both guys have enough time to work out the script. If they haven't already begun working on it.
I remember reading an article somewhere where Singer was invited to a dinner with Alan Horn where he basically layed out what he had planned for the trilogy. Some time later he was accepted as the director of SR.
Now they could've just had a a simple plan like for example "In the first movie , we'll just have Superman saving the earth and lex coming up with a devious plan and in the second movie we'll have Zod returning and in the 3rd movie we'll have Braniac.".
That or they have already begun writing a concept for the sequel. Action scenes being fleshed out etc.
Besides it's still 3 years till 2009. I think that singer will take the same approach that he had with the X-Men movies and SR which is going to be shooting the movie somewhere in 2008 and then use the other time for the VFX. Don't ask me why he would do that , cause i don't see how a big budget blockbuster like Superman with massive VFX sequences ( hopefully with a villain this time around
) will need a post. prod. schedule that is less then a year.
But anyway going back to the writers , i think both will finish their movies somewhere in 2007
I,LUCIFER ( which btw sounds like a awesome movie !) doesn't have a release date , but i think Craig will begin work on this movie after he finishes work on The Golden Compass. Or not, because the sequel to Casino Royale comes out in 2008. So i think that movie ( bond sequel) has a higher priority .
Which would mean that by the time Craig finishes up on Bond , Harris will have been contuining working on the script alongside Dougherty.
Trick 'r Treat comes out on the 5th of oct. 2007 ( taken from IMDB) so Dougherty will definately be finished before 2008.