I for one would not mind BV continuing as long as the writers, producers and the channel think that they have something to offer to the viewers worth their time.
The very fact that BV, even after 6.5 long years continues to grab the eyeball of viewers, whether by force of habit or due to its understated yet generally effective manner of storytelling, which is way different from many really loud and unrealistic stories being told on TV, is a feat in itself.
Balika Vadhu, from the time of its inception has been a method of story telling that believes in showing the after effects of ongoing old-fashioned traditions, hoping to make the people sit up and take notice. Which is why they started the serial with a small girl getting wed at a tender age and how this one action affected her entire life.
While that story has nearly come to its completion, that girl's connect with the audience is what the writers hope to use in order to tackle other issues.
Current track involving Nandu is another case in point. It is a good and valid issue not handled earlier.
So long as the writers have these societal issues that they can effectively relate through their protagonists, Balika Vadhu can continue.