OK if Kaguya had died will it set of a chain reaction. She has the original Sharingan DNA cells which hold within her. Since she is the original, and she die. Will other's Sharingan users DNA cells die off too ( sasuke, salad). it will not kill them but they will no longer have Sharingan DNA cells, but they will have a Byakugan DNA cells because they will be free from the sharingan curse.