Hi everyone, just in case you want to know, there has a been a Petition created to sway M$ to make there Xbox 2 (Xenon, Xbox Next, etc.) backwards compatible with Xbox 1 games. http://www.petitiononline.com/xbox2/petition.html 22852 Total Signatures as of my signing.
Well, because microsoft is smart, (well, kinda) you will probably need to wait for a Xenon chip before you can play your backups on it.
It may take a while to get a chip out (expecially if the guts of the Xenon are far different from the XBox) but, if all goes as "planned" i believe that the first chip will be out Summer 2006 assuming that the Xenon comes out Fall 2005.