you know like the second generation nearly all the characters left, apart from SAHIL, Gautam & Harsh from the original photo.
i think once Boomi-Joydeep gets married will probably desapair.
Mohini Daugther looks certain leave. about a year or 2.
i also feel Nakul is going to desapair as well.
That leaves with:
Manthan- Since he's Karans son(who was the main protaginst of the 2nd generaton) and his character has grey shades, i think his character will stay till the end.
Lakshya- If he is Krishna Tulsi Love intrest, then his chances of him staying till the end is very good, But if he is not then he is likely to despair.
Eklavya- Definently going stay.
Mayank- if the rumors are true that he will marry Krisna tulsi, then he will stay.
Krisna Tulsi- will offcourse stay till the end.
The people who are yet to come are offcouse KARAN-NANDINI child, who is also likely to stay.