Como supondrás no puedo asegurarlo por experiencia propia, pero en las FAQ de la web http://www.blu-ray.com afirman:

"Will Blu-ray support playback of DVDs?
Yes, several leading drive manufacturers have already demonstrated drives for consumer products such as video recorders that can read and write DVD and Blu-ray Discs, so you don't have to worry about your existing DVD collection becoming obsolete. Although there is no requirement for Blu-ray recorders to be backwards compatible with DVD, the format is far too popular to not be supported. With the vast amount of Blu-ray recorders that will be coming out, this will be an important feature for consumers".
Por otra parte el HD-DVD desarrollado por Toshiba y Nec tengo entendido que también utiliza el laser azul-violeta.