Why does everyone seem to think that a massive chunk of the cast we've seen so far will be unlockable? That there will be unlockable characters at all hasn't even been confirmed, and given that Sakurai is all down on internet spoilers, I consider it a non-trivial possibility that the whole roster will be available from the start. Even if not, it's by far the most logical that everyone we've seen is a starter and that the unlockables are all characters we haven't seen. The only possible exceptions are third parties since Sakurai can be weird, but I read a lot of complaints online about buying Brawl that advertised Snake and Sonic and then not having access to them so I wouldn't be surprised to see that change.
Non-trivial? Logical? lol, I'd say it's more logical to
assume there will be unlockables as there have been unlockables in every previous installment of Smash. Of course, it is
possible that there won't be any, I'd wager you'll be incorrect. Didn't Brawl's dojo show us Ness, Captain Falcon and a handful of others before release, who were unlockables?
Sakurai wanted to make these character trailers to hype development, rather than save them all for another Subspace Emissary type of thing, because people can watch the videos online. But he didn't go as far as to say that would go for all unlockables. It would be no fun if you had everything from the get-go, unlocking has a charm to it.
And if there were no unlockable characters, why pick and choose what is unlockable? It has already been confirmed that Equipment/Alternate Special Moves will be unlockable (i.e; you'll find them in Smash Run, or maybe as items in fights like stickers/cds) why not give us all that from the start too?