As much as I don't want it to happen. All good things must come to an end. Well if the story ended, we all know Haruhi will just create a new world again and it will start over from the beginning. That is if she wants to.
Anyway I'll write my preferred ending and my predicted ending.
My Predicted ending. A very anti-climatic end.
Haruhi, As she finally accepts a normal life. She wouldn't be displaying any signs of her powers. She will still be going around with her search but in reality she has already accepted it and will be happy with Kyon. Haruhi the most powerful Housewife and still the honorary leader of the SOS brigade.
Kyon. after seeing Haruhi's change of heart (and has grown her hair back). He accepts Haruhi's confession (well it has to happen sooner or later right?). Kyon lives a somewhat normal life as a writer and writes a book about a Guy who met a Girl who has a very unique personality that will change his life forever.
Yuki. She has finally become as normal as she can be. When she has decided to severe her link with the Intelligence-something-Entity. There was a struggle between them but they were finally able to convince this Entity to leave her alone. Lots of help from Asahina and Koizumi (and secretly from Tsuruya and Emiri). She becomes a freelancer programmer and a full time librarian in the local area. She still helps Haruhi with her search
She goes back to the future heart broken but now determined than ever to become a dependable woman. We all know what happens afterwards right?
After losing his powers. He works full-time for the organization and now moves under direct order of Tsuruya.
I'll write whatever happens to the rest later and my preferred ending as well.