I have been on IF for quite some time and I have become a lot more active over the past years. I started as a reader and then as a writer of Maan and Geet stories. I have to thank Geet forum for my success because a lot more people read stories there then they would in Fanfiction forum (This is true till date!!!). And I am not the only one who could promote their stories because of the respective forum. Plus, there is so much activity in the fanfiction forum that one can hardly keep track of all the stories. Even the efforts of people to track of writers and stories are failing.
Another point is that there are a lot of people with unfinished stories who have exams, are working or are otherwise busy. They will probably not know about the closing of the forua and hencewith their thread/s.
Saying this, I can understand your point of different fora but to be honest it is far more difficult to keep track of different fora and connect to people there if you don't know anyone. In one forum, you know that you have like-minded people present and can connect far better.
I hope the your decision is still not final and there is room for negotiation. I am sure a lot of people will leave IF if their respective TV serial fora are closed because they will not be able to relate to other fora. It will be sad for IF as well as writers like me who will lose readers. From other threads I also heard people moving to blogs and leaving IF. This will have the opposite effect and also make them lose many potential future readers and will devoid us, at IF, from fabulous stories.
After all, many stories are written and people stay connected even after the serial going off air because of the high activity in the respective fora!
I hope there is something that can be done.
Mina