According to 343 Industries boss Frank O'Connor, "There's some fairly radical modifications to his armour. Some of those are an artistic evolution, but some are connected to the story. We just can't talk about it yet. He's been in space for a long time."
Another development is something that was hinted at in Halo 3: Cortana is beginning to enter the stage of her existence in which there's a chance she'll go rampant.
"Seven years is the lifespan for a smart AI before it enters a state called rampancy," explained O'Connor, "Cortana was getting close to the end of her natural lifespan at the end of Halo 3 but she has been exposed to far more information than any other AI in existence. She's going to develop some muscle from that process but it also contributes to her rampancy - that much information makes things worse."
Halo 4 is due to be released on Microsoft console in late 2012.
