My biggest concern for Bitcoin Cash, my nightmare even, is that Core decides to raise blocksize to something still unreasonable (like 8MB) but enough to kill BCH.
The differences are more extensive than that one parameter. There is so much added to the protocol by the Core developers that hamper it's ability to scale at the base layer.
The nightmare persists. Enough useful fools exist right this moment. There would be exponentially more if BTC fees ever become as cheap as BCH (even for just another year or two).
