it really depends whether longer term investor interest develops for BCH. if it's being purely manipulated and bitmain (and friends) are just buying into everyone's dumps, then they will just be left holding the bag, and the problem will sort itself out.
if, however, they are successful and maintain status as a top 3 coin competing with BTC, they could really split prospective BTC investors, cutting down on the money flowing into BTC. if this happens, there is also the slight possibility that BCH would overtake BTC entirely. that seems pretty unlikely, though.
but the emergency difficulty algorithm adjusts it back down very quickly. isn't it something like 6 blocks? whereas adjusting difficulty upwards is just like BTC (~2 weeks). that means that this cycle could continue for a while, until BCH buy pressure is totally exhausted. the EDA can basically cause hyperinflation for BCH under these circumstances.