Any chance they both just continue on? Does it have to be one or the other?
It can happen but at the same time with the fork coming on November we will have in theory three different coins, to me there is no room for three coins calling themselves bitcoin, one needs to die and even if the 2MB fork has not happened yet, bitcoin cash looks like the weakest of all three, so if bitcoin cash does not disappear in the next weeks or months then it could disappear in the next year.
Excellent prediction, agree with you and moreover I think it's useless and requred only for political struggle inside BTC Dev team.