No matter how we may think that it is or isn't a media center mac, the fact of the matter is that it's damn near perfect positioning for such a thing.
1) right price - this is half of media center windows machines, and working into tivo range. Certainly, with the combo drive.
2) Airport express - look, speakers all over.
3) software - the list just goes on and on.
iTunes (home stereo now, with the airport express),
iTunes Store (buy your music right from your TV),
iTunes Movie store (remember that whole video thing? I smell direct home delivery of movies)
iPhoto (quickly imported from your new iPod Photo),
iMovie for quick edits,
iDVD... I know it said it didn't come with it, but I bet that's on the combo drive model.
4) bluetooth possibility - yes, it's not mentioned, but BT is cheap stuff to add which would work nicely if they included bluetooth on the..
5) iPhone - now you got a remote.
Of course, I agree, it needs more disk and more ram, but that's what upgrades are for. My money is also on them getting a license from tivo (it already does rendezvous) and getting channel guides, or running their own.
Even if it is not said to be such, I think it'll be an excellent choice for such a thing.