As much as i want them to be together again, i know its a little bit difficult for that to happen -- though not impossible :).
Yes, we do have filmmakers roping in the same actors repeatedly to encash in their chemistry...but movies are made at a length of 3 hrs only. So if the audience like the pair, they are left wanting for more...and thus producers try to rope the same actors for different movies.
However, a tv serial runs for months and years...that too on 5 days a week! So its a obvious that the audience are getting their daily dose of their fav, actors unlike in movies.
So when a show repeats the actors again, the audience feel a little bored. The hardcore fanbase would never be bored ofcourse. But the TRP generating audience does feel bored to see the same actors again and wish for fresher pairs. And the producers, who make shows for money, do value trp generating audience more and hence try to get fresh pairs.
Hence, most of Popular TV couples are not repeated again. Some do get a chance. Eg. Hiten Gauri...and our AviNa and we should consider ourselves lucky that we got to see them twice together, whereas other Couple's fans' are still trying to get their "Fav Couple" together even after so many years :)
Having said all this, I still truly wish that AviNa do get a project together :) See nothing is impossible. There was no trend for shows to return with sequels, but CB did make a comeback...so who knows...perhaps even the telly couples will make a comeback together :)