I will speculate that Onir will be framed or either be blackmailed by Mittal and company in the untold scam that is yet to be revealed.
The framing/blackmailing will come because of the surveillance video that the doctor has showing Onir swapping babies. As a result Onir may end up in jail or killed. Purvi will be left alone still in love with Arjun and will continue to live alone for a number of years like archanna did when Manav went to Canada. thus upholding the pavitra rishta between she and Arjun.
Arjun will find out that the baby he and ovi has is really purvi's child but will not find out that it is really his and purvi instead of Dr. Onir and Purvi. Life will go on as usual between ovi and arjun and maybe purvi will get to see her baby from time to time as she will not take the baby back from arjun/ovi.
New stories will develop with soham and teju/sunny. Then some other drama will be forthcoming.