I'm thinking the BETA will drop right after E3 which is June 10th-12th and before Bungie day on July 7. They have mentioned before that they will treating the BETA like a full on launch. I can see Bungie pulling back the curtains on the game, announcing it during E3 and possibly having private test sessions for press and gamers during E3. Also remember that summer officialy starts June 21 and they have repeatedly said "summer 2014"... So there's my theory.