Just as there will be no PCE CD games on the VC, there will be no Saturn games either.
Shouldn't it be pretty obvious, considering they're only using cart based games? It'll remain like this forever, no doubt. A CD game cannot fit on the Wii, and no - they will not re-program the entire game just so that they can replace CDDA/high quality audio with compressed audio, they won't!
They might update the VC to run games off memory cards or give the next hardware revision somekind of larger or exapandable internal memory.
Look at all the crazy evolutions of hardware, software and accessories in the past from all consoles.
Its true that they didn't reprogram the first GBA to have a backlit screen, but they did make the SP & Micro.
I don't think the Wii/VC will probably get large/CD game support, but it's far from an impossability. If the VC makes Nintendo a billion dollars, they'll find a way to get it to make them a billion more.
If the Xbox360 could receive an external HD-DVD player, I don't think that an external hardrive at the very least is so far fetched for the Wii.