It's only the end if you want it to be darlin'. You can read the books and watch the movies as much as you want. I know I'm going to. I'm not ready to let go of Harry Potter yet. When I read the books over again, I still feel as happy and excited about it as I did the first time I read them... And that is good enough for me.
I know there won't be any new Harry Potter stuff after this movie is done, but I don't feel like there needs to be.