In March 2007, Boyle announced plans to create a third chapter of the film franchise, which will be given the title 28 Months Later with a 2009 release date,[34] thus creating a trilogy. Boyle has stated that his thoughts are to set the movie in Russia.[35]
In June 2007, it was announced that if DVD sales of the film did well Fox Atomic would consider producing the third film.[36]
In July 2007, while promoting the film Sunshine, Boyle revealed that he has a story formulating for the next film "There is an idea for the next one, something which would move [the story] on. I've got to think about it, whether it's right or not." Boyle also revealed that he would return as the director.[37] Alex Garland might be considered in writing the story with Boyle, but no announcements have been made.
http://en.wikipedia.org/wiki/28_Weeks_Later#Sequel
I hope the third one takes place in a really post-apocalyptic world. Not have it just England based, but show another location entirely. It'd also be nice to have some of the cast members from both "Days" and "Weeks" coming together in the third film.