I am sure that most low-quality coins will no longer exist in any case. But 90 percent is too much. May be 70 percent will die because of its poor functions.
I think it will only arround 20%-30% coins will die, because there's no update in their product and no active trade. 70% is still too many, if there are currently more than 2000 altcoins on the marketcap, then around 1700 coins will die. It can't be that much of those who are bad.