Actually Nintendo was planning on having DVD playback on the Wii accessible by a DVD dongle accessorie (which presumably takes care of the issue of licensing fees, since it's off loaded onto an accessorie).
They scrapped this likely because by 2006/2007 most everyone who needed a DVD player already had one -- or two or three in their house.
But they could theoretically do this for Blu-Ray again. It would free the main system of having to pay Blu-Ray royalties and off-load the cost only to people who want that functionality.
Microsoft did the same thing with the original XBox.
The thing about Blu-Ray is over 4 or 5 years it's probably going to be the cheapest format for Nintendo because it'll be heavily mass produced by several vendors and Nintendo isn't tied to one vendor.
You go with a completely propietary format (like say holographic discs) and that company is really the only one you can go to, whereas with Blu-Ray lets say Samsung is giving Nintendo a better price than Panasonic ... they can go that route.
