I think Dhruv will be back but as someone else. Maybe he'll be badly scarred in the accident and have extensive plastic surgery and obviously memory loss. He'll come into contact with the Raizada family and feel a strong connection to them. Eventually he'll work out he's Dhruv.
Or Sachin could come back as Dhruv. Maybe he will have amnesia, Sundari will find him first, and convince him she is his mom and the Raizadas treated her badly, etc, etc. Dhruv will take revenge on them, but finally regain his memory.
Or maybe Dhruv will pretend to have amensia to catch Sundari out and take revenge on her!
I don't think Vedika will marry anyone else as she has to keep up the facade in front of the rest of the family.