BCH will never replace BTC. The reason is because, as of right now, new adopters of Crypto are MUCH more comfortable with BTC than any other currency and as of right now, new adopters are numerous and VERY important. However, in the future when new adopters are few (or non existent) I do believe that BTC will be surpassed by another currency. I know that this currency will NOT be BCH because by this time in the future, there will be countless currencies better than both conventional BTC and BCH. In fact, I do not believe that the superior currency in the future will even be a fork of BTC.