What was the market saturation like when it was DVD vs VHS? It took several years for DVD to become dominant over CHS. With BR vs DVD however it is different whilst there is an improvement in picture quality with BR, for many DVD is good enough. So BR is finding it harder to establish itself than DVD had over VHS.
That's why I still think that Bluray will not (at least not for a very, very long time) replace DVD as ubiquitously as DVD replaced VHS. There's just way too much they have in common. The picture is the only difference between these while the differences between DVDs and VHS are huge.
Sometimes a Blu-ray can just be superfluous and unnecessary. I've really tried to understand why people think it's such a huge difference but I just don't get it no matter how much I try and no matter how much I watch my friends' BDs on their HD TV. I couldn't really care less for the higher definition and the augmented sharpness and contrast.