What i think ekta knows that k-n are trp booters after smirti's(tulsi), so she is concentrating on them, i think if they die dramastically ,
1. May be they are not dead saved by tulsi or smirti..
2. If they are dead means ,for reincarnation it takes so much, so meanwhile k-n kid will come., tany becomre more evil .. so that time i think humshakal Gauri will be introduced with new character name in younger generation where k-n kid or someone sees either karan or nandini ( humshakal).. so there will be death to k-n characters not hiten & gauri & now they will play younger generation with may be anitha..hiten,gauri.,, also...