Xbox 360 supports usb software, such as the keyboard. Never heard of anyone hooking up a mouse to one before, though its not outside the realm of possibilty. Besides which, if they can get a game like Classic Doom to operate smothly on it, than they shouldn't have any problem running Arena or Daggerfall.
:read:
Microsoft won't allow any unofficial USB connectables to work on the 360, from Keyboards to Wireless USB cards. On the PS3, they have released a Keyboard and mouse, but I doubt Bethesda will alienate 90% of the console market without a Keyboard and mouse to suffer with a broken game.
As for Doom, ID software has released it's source code in 1997, making ports possible, Bethesda has apparently lost the source code to Daggerfall. Not to mention ID software updated the Doom engine and made it more versatile when it was ported to Windows (due to it's popularity), Bethesda hasn't updated either Arena's or Daggerfalls engine to make it simpler to use in a modern computing environment. Not only would Arena be impossibly difficult to port, but Bethesda and many other people simply don't feel the need to do it.
Just because an old game got ported doesn't mean another one can, many things change between the two engines and games. I'm sorry to say that a console port of either Daggerfall or Arena is pretty much impossible.