Ok everyone so here is my take on this:
1) I agree with Shyamala who has been writing excellent posts...ARVI is ultimately going to happen.
I know a lot of people have been bashing Arjun but keep in mind sthat he was taken by complete surprise in front of everyone. It also looked to me like while he was looking at Purvi somebody literally lifted his hand and Ovi stuck the ring on. I noticed throughout the entire segment he looked extremely shocked and unhappy. He didn't get a chance.
2) The engagement may have happened but the marriage will not. Yes it will be tough few weeks for Purvi as well as for all of us. But ARVI is the track just like Archu/Manav. Ultimately they also did not end up going through with marriages to others,
Also, even though Purvi is upset she will have to stay strong as Arjun had to when he watched her with Vinay. Even though there were no confessions he had to watch and couldn't do anything about it.
I think Ovi will find out and unfortunately she will end up turning into a negative character. I still have hopes for Teju though. For some reason I get the inkling that she is going to play some part in our favor. Ive watched her in the last episode and the way she was talking she definitely was not at all convinced about Arjun's feelings for Ovi.
I think when Archu comes to know she will stand with Purvi. That's the funny thing with twins and a different story track too that will be very interesting, Teju is so sweet, humble, adventurous and endearing while Ovi looks down her nose at the language, idea of staying in crawl,wears skimpy clothes, etc. Archu already was shocked at her pics, inability to wear sari, and if she maintains this attitude Archu will find it tough to relate to this daughter of hers.
Arjun will do something...I am pretty sure of it...but u have to see from his shoes...it was a total and complete shock of unexpected proportions. Also keep in mind Purvi's dignity...he cannot expose her in a public setting like that in that moment...u guys have to realize that it would have actually been very damaging for her given the circumstances of everything.