I will be happy person if Naagin is going to have an extension, but personally don't want the extension to be more than 15 episodes in any case and as I also said it earlier...in my POV they have enough story, suspense and lots of mysteries to extend it by near about 15 episodes with show story remaining tactful and captivating right till the end...and without butchering, compromising on quality aspect and any kind of negative effect on the show.
I also don't want any negative energy surrounding the show due to unnecessary extension/stretching.
And regarding second season...I will be OK with both situations...if it really comes back with same main cast, am gonna be happy...but if there is no second season, then also am OK with it...personally no issue whatsoever reagrding season 2 of Naagin
Regarding 24 season 2...it is going to replace CNWK...CNWK going off-air from 17th Jan, 2016