I think you might have to spend extra for blu ray of any movie in the near future, As I hear, Blu Ray will replace DVD as DVD replaced VHS. So when they stop maing DVD...
This is what I think will happen, if I'm wrong then let me know. The local Best Buy stores are allready expanding their Blu Ray section and minimizing the DVD section.

But not everybody has hi-def yet so I seriously am getting confused now on what will happen.