I wouldn't expect DVI / HDMI cables any time soon, not even (cheap) third party ones.
Analogue to digital conversion is extremely hard, nothing like converting Svideo to composite, or even transcoding component to vga (which is pretty hard to do right). DVI/HDMI support has to be put in the system from ground up, coming up with a cable later that would do the conversion is much harder and more expensive.
There are VGA/Composite to DVI convertors out there already, but they require a hefty amount of electronics, external power sources and will set you back $600-$800, so it's not about just soldering a few wires. MS didn't release the cables in launch and will not do so.
It's a big design flaw, if you ask me, but what can you do?