(i thought we had a thread on this, but i couldn't find it. I guess i was wrong?)
Yup, it's official: a sequel is going to happen. Here is the plot synopsis:
"The film picks up six months after the end of the first pic, in which a virus spreads, leaving few survivors. Special Forces is working to restore order and helping repopulate London when a carrier of the virus unknowingly ignites a reinfection."
Eh, i was leary at first, but: Alex Garland is writing the sequel as well. The directors? Not Boyle, but a guy named Juan Carlos Fresnadillo is taking the reigns. Apparently, he's a pretty good indie director.
Lastly, Harold Perrineau (from LOST) has joined the cast as a Helicopter Pilot who brings families back into London after they believe it's been quarantined and fixed.
Movie is aiming for a release of next summer, I believe.