If it was not obvious months before the 360 was released when they first told us there would not be divx/xvid support then it should be obvious by now that they have a revenue model for video that they would have a very difficult time marketing to movie and tv studios if the 360 was capable of playing divx/xvid natively. Only formats with a decent DRM system built in will ever by openly supported by MS since the suppliers of the content will want to have some control over who can play the content and for how long. 100 points and you get to watch some TV episode.. 400 points and you can rent a movie (video expires in a week or so). Video served and instantly paid for by a marketplace already on the 360.
I think the resourceful owner will find workarounds and hacks but for MS to openly support xvid/divx is not likely. It is naive to think that any pressure from us will turn MS around (after all the market is full of divx/xvid capable dvd players) so better to just wait for the inevitable hack/chip that will finally unlock the 360 to its full potential.
Personally I cheer the constraints that MS places on the 360..... the more incentive that the hacking community has to unlock the box the sooner it will happen.