Doubtful, since he’s Sega’s Chief Creative Officer he’s kind of obligated to go. He attends every year to check out the new games/consoles and have meetings.
Nagoshi is not just the Yakuza series producer he’s actually had a hand in most of Sega’s biggest games including Vanquish, Monkey Ball, Shenmue and F-Zero GX (among others.)
Sega just recently announced their E3 lineup and unless it is announced at the Sony conference Yakuza 5 is not on the list. I suggest leaving a comment on the Sega blog or Facebook page to let them know what you think.