So far it's probably JUST the IBeLink DM11G units pushing the hashrate - but by the end of October when most of the currently sold but not yet shipped Bitmain D3 units are shipped installed and running, we're looking at a LOT more than a "doubling".
Then the A5 (and probably more D3 and some DM22G) units start hitting.... I'd BET on network hashrate exceeding 200 TH by the end of the year, and would not be shocked by 300-400 TH.
I'm not sure what that works out to in difficulty as a number, but I'm sure it will be 5-10 TIMES what it is now by the end of October and likely double again by the end of the year.
Seems very plausible. Assume also existing miners will drop off as feasibility rapidly decreases and current asics takeover.