With blockchain split or not, I am sure the new block structure allowing for more transactions will cause fees to drop, which would be great news, because they have been too high for too long imo.
But in case that happens, you think it will last for long? Will we be able to enjoy small fees like we used to in the good old days for a long period of time?
Transaction fees will drop until the number of transactions increase to fill blocks again. Segwit is a temporary solution. We may be only a few months away from having full blocks again.