Hey guys, I just listened to this week's gameblog.fr podcast, and Julien confirmed he ALREADY saw MGS Rising running when he visited Kojima Productions in April. He couldn't say anything of course (NDA...) but he thinks the game won't be playable at E3, but there will be a trailer. He then added that what he could say is that the game looked "really nice, really really nice" (or something like that ^^), and that you shouldn't ask him whether he brought with him footage of the game (meaning that YES he must have footage of the game, ready to be uploaded for E3 I guess).
If some of you don't trust the source, you should know that they are the only journalists I know of that were allowed to visit inside Kojima Productions (here's a picture of their meeting in Tokyo, you can guess Kojima doesn't do this for every journalist:
http://download.gameblog.fr/images/blogs/10/6962.jpg)