TWO things to consider here:

1, Segwit is ready to be implemented. The process to enable segwit was two parts: first, Bitcoin updated the software. but second, segwit upgrade was never executed. IF bitcoin core group can come to 100% consensus and enable segwit, realistically bitcoin value will surge. If they do not, then you are likely very correct in your assumption that the mempool will get bigger and slower and the world will not wait for BTC--it will go to litecoin or Bitcoin cash.

2, Coinbase added Bitcoin Cash today. I am a firm believer in the Coinbase Bump: all coins offered on coinbase increase in value because of the exposure (there are only 4 coins to choose from on coinbase). Coinbase has not enabled selling of Bitcoin Cash yet. Many users on coinbase were using the platform in August and will discover that they actually have some bitcoin cash in their wallets from when the hardfork took place. When coinbase enables selling in the coming hours/days, many coinbase users will sell the Bitcoin cash since it is around an ATH and they will view it as "free money". this could create a dip and be a nice time to buy.