Since this ASIC was released the difficulty hardly climbed that much. Back then people were assuming we would get crazy jumps in difficulty and most were scared to make the purchase.
I seriously doubt there will be a diff climb because of these miners. They aren't more efficient than GPU's.
The difficulty will not increase because it was already mining for bitmain. Bitmain is just turning them off, putting in boxes and delivering to the buyers after 4 months. The difficulty doubled in 1 month and the asics are the reason for that cause it was viable to build and put them to mine at that time, also pay attention that difficulty is not increasing right now cause there is not much to gain from it, so bitmain is using their resources where they can get the most from it and ethash is not on that list.
The f3 while is 10 times the hashrate of a the e3, is not worth x other algo which can give bitmain a lot more money at moment. Selling the e3 was the best thing bitmain ever did, clear the garbage inventory and at same time use that money to build other profitable things.