This is just a speculation on "what if's"
Link to follow : https://bitcoinexchangeguide.com/after-51-attack-high-transaction-fees-on-ethereum-classic-keep-investors-cautious/
Anyways, since the fork is coming up (but a little bit delayed), I think this could help increase the demand for ETH to receive the forked coin.
I don't think there will be a separate coin from the unforked chain, at least nothing worthwhile. As far as I'm aware Constantinople is a non-contentious upgrade, so everyone will follow the new chain. There will always be someone who claims to have a viable new coin following any fork, but I can't see any new variant being sustainable.
This is about the protocol update.