haven't u seen the last 2 diff %? also s3 and s4 will come offline in the future. some farms may even close forever, some may burn down, etc etc....
Estimated Next Difficulty: 39,395,957,236 (-0.16%) after more than a month of hashing, s5 are going in the box for shipping!
Its unlikely the S5 have been hashing for a month, at least not in large quantities. Likely bitmain had batch 1 (and maybe batch 2) in testing for som time, but likely only a small number of miners (<5PH) would be testing/burning-in at once. but the fact is that bitmain more likely runs an S4 farm or has/is developing an S6. Its insanely easier to monitor, install, and control a hundred devices than it is to control 4-5x as many.
diff is looking high on varience again (possibly due to short testing periods for new hardware, plus paycoin users switching back or turning off) - around 1% this jump seems likely, maybe 2%.