Halo 5, BO 3, best sports season in USA (NFL, NBA, and world series) a few weeks after hard mode release and 2 months in to an expansion cycle. A natural lull is going to hit any game, this isn't WoW where you must grind eternal. I expect less players to be on from here until the next expansion. A game is dead when no one buys the next expansion or release, not when it has low players.