kozikowHistorically, MassDrops have been 2-3 months apart (January, April, June and August). Due to supplier issues this time around they probably won't launch round 5 until they find suitable replacement suppliers for the slowest ones from this round.
Round 5 probably won't be until late November at the earliest but probably more like mid-to-late-December with fulfillment in 5-8 weeks (mid-December to late January or early February).
Of course this is simply a educated guess, based off historical data.