I don't think it'll be instant dead. Most of the exchanges today won't support it, but that doesn't mean other exchanges will, new ones will come too just like with any other alt coin. Bitcoin cash will take time to adopters, it may be huge in some time, or it might be like a secondary currency much like other mayor alts.
As will all forks of any stocks it will split the price into two
Bitcoin will be valued at half of what it is now and this bitcoin cash will be valued at the other half.
Then if there is support for it (AT ALL!
) it will either keep it's value.
Or it will just wither and die.
Remember what happened to ETH when it was split by the DAO into what it is now and ETC?
Same shit.
Just different pile!