A spokesman for Aardman Animations told Reuters this about the chances of another Chicken Run...
"We are not going to consider a 'Chicken Run II'...the studio's next movie will be an Aardman version of 'The Tortoise and the Hare' - a 'Tortoise and the Hare' meets 'Spinal Tap'". He also confirmed they'll soon work on a "Wallace & Gromit" feature, but "Those productions will occupy us for at least the next five years...there is of course pressure for a 'Chicken Run' sequel but right now it would be impossible"