I can understand why MS says no to a blu-ray addon, it would not come cheap (develop, sell, market etc.) and if they did put games on blu-ray everyone would have to buy one to be able to play the new games, so they would have to make new 360-models with blu-ray instead of dvd, and sell the "old" versions cheaper. A lot of customers would too be mad because they would have to buy the addon.
To little, too late is blu-ray for 360. Most games still is fine on a dvd-dl, and in orst cases yu may need 1 or two more, no big deal. Especially since those games that requires a lot of space mostly is j-rpg, not you're ordinary, mainstream action or rpg-title. Wii sell's like mad and doesn't have blu-ray, Wii2 will probally neither have it..
The next generation of xbox on the other hand, is in dire need for something more than dvd-dl to fit the games. Until 2011-2012 we can cope with one or dvd's, but after that there is no future in using dvd's any more, since games would require such a vast number of discs (still remember those PC-games with 7-9cd's). Blu-ray is one option, a big harddrive and the ability to download games is also possible, but neither practical nor useful for everybody. Blu-ray, hd-dvd, Terrabyte-dvd, memory-sticks, memory cards?
Something bigger than a ordinary dvd is required, or a multilayer-dvd (those are expensive and bad quality too) is required. That's a fact MS knows, and the next generation will show us how they've solved the problem. Blu-ray for this generation would be fun, but not necessary, neither required or worth the money I think.
Media extenders like pocornhour, WD TV or Xtreamer (better then WD, with mkv, subs, .ISO etc) is part of the future. If you rip the movies, or download them (legally) is your choise, you can buy a blu-ray too if you want. But media extenders will always be smoother, faster and give more, the only thing they lack is the ability to get new movies fast, cheap (and legal in most cases).