I personally prefer Ayaan or Humaira to raise Seher but as we are not sure of their characters being continued after leap, my guess is as below:
Dilshad will run away to Punjab with Sanam and Hiya as she is shaken by death of her children and will go in to disguise to protect identities of her grand children for their safety. Hiya seems to be deaf and dumb, therefore, Sanam will take up the financial responsibilities by running the dhaba.
Seher will be with Razia. After hearing the news of massacre, Razia rushes to SM to collect Gaffy's dead body and when she realizes ASYA are dead and Dilshad and other kids went missing, she comes forward to take care of Seher and the business as Razia is business savvy and lonely. Saher will have the modern look ( opposite to Sanam) and grow up as a shrewd business women under guidance of Razia.
PS: While, I am not sure if Ayaan role continues after the leap but if it does, it will be interesting if he takes up responsibility of Seher either taking her to London or coming back to Bhopal to take care of Asad's business and Seher. Even HAIRA would be an interesting track.