Is it me or does it seem like Sakurai is just announcing every character instead of only starter characters? For one, if it is starter character only updates up till release, we have A LOT of starters. Second, wasn't Snake stated as being unlockable? Maybe they put an update out of him cuz he was previously announced.
For Melee, he didn't start showing hidden characters until after he showed every starter character. Also, when he started showing the hidden characters, he said that they were hidden and told how to unlock them as part of the update. I think that that's how he'll do Brawl too. He hasn't said anything about hidden characters in any of the character updates so far, so I'm pretty sure that all of the characters that we've seen so far are starting characters.
The people who say that Snake was already confirmed as a hidden character don't know what they're talking about. Sakurai never said that. He said that he thought guest characters, like Snake, may be better suited as hidden characters. He probably changed his mind about Snake, because he thought it was stupid to waste a hidden character spot on a character everyone already knew about.
Sakurai may not show any hidden characters until after the game comes out, but I'm pretty sure the entire character list will get out some how before then.