Don't trust what im about to say, due to the fact that I don't work for Nintendo,
If they were ever going to add on a 'Blu-Ray' player onto the Wii console, I'm 99% sure that they would more or less revamp the entire system and then re-do it. Fixing previous flaws, and adding new ideas, such as Blu Ray. If you expect Nintendo to magically whip out this new DVD drive onto existing consoles, I wouldn't hold your breath.
I personally wouldn't expect anything that major until the next console comes out, and by then, there'll be something bigger and better they can add.