Kojima mentioned that when he released Peace Walker, it was "an experiment for the cloud computing future." Ultimately, Kojima says, he'd like to let players start a game on their PlayStation 3, then take it with them on the NGP while they're away. When they come back home, they can continue the game again on the PlayStation 3.
"This dream is going to come true in the near future," he said. "And right now, I'm working on this project of the dream. I'm sorry, I can't reveal this now. But we'd like to present what we're doing at E3."
[Ed. Note: Image above from PS3 version of MGS4]