Obviously karan nandini r to come back, because they just rolled and rolled off... if they were actually dying, ekta wld show their faces, as she showed tisha, ansh and savita's face when they died. They did this mainly because some mastermind thought...if karan nandini comes back, it will not be fair on manthan as he loves 'tanya mom'. So they made him a so-called-murderer so that their return to sn is justified. Ekta will try to convince us that they are dead by showing 'diya bujh gaya' and will show flashbacks, and will bring them back after many days, to keep us in suspense.
Ekta loves money, and she knows without karan nandini, less money, less viewers, falling trps! so watch out!