Currently what is being showcased in the show is that Dev and Sona have too much bitterness and misunderstandings between them. Some caused by themselves and some due to external factors Ishwari, GKB, Vicky and Bijoy. Love was never a cause of rift between them. In fact they were madly in love with each other and actually that backfired on them. Dev and Sona could not meet expectations each had from the other. No relationship can sustain on love alone. Sona was constantly bashed for being misfit in the family and Dev never took a stand for it. Dev wanted her all for himself forgetting that they once married there are many factors to take care of for the smooth sail of the relationship. All he gave importance was to Ishwari and her feelings. In doing that he didn't even care about Sona or her family. Dev could not balance it out well nor Sona in some ways. She too hid things from Dev and Ishwari be it Vicky-Elena affair or starting a new business or poking her nose too much into Ranveer-Neha matter.
Mistrust, lies and frustration was building up amongst them and after they came back from Shimla all hell break loose. GKB and Vicky's evil planning led to tussles between Ishwari-Bijoy, Bijoy-Dev, Sona- Ishwari, and finally Sona-Dev. All the frustration, lies and bitterness came out in a very extreme and ugly way which led to their separation.
Both went separate ways accusing each other for the rift. Dev thought that even though he was faithful and loved her immensely Sona left him. So that led him to lose faith in love and he turned the opposite. Sona on the other hand turned more fierce and a strong woman so that no one can play with her emotions again.
So if we think logically both still have a chance to unite if this time they both act wisely and have a more transparent relationship without any lies, miscommunication and with trusting each other and not allowing any third person to come between them.