User blog comment:Master Sima Yi/Assassinews 19-03-'14 – Two Assassin's Creeds for 2014?: Unity and Comet/@comment-413232-20140610175943

There still hope for AC Comet. Assassin's Creed content for old gen will be announced later according to Yves Guillemot (CEO of Ubisoft):

Watch this interview at 1:53

Maybe they didn't want to diverge the public focus from Unity and the next gen during the E3, so they keep Comet announcement for later.