^Yeah, that occurred to me too. Perhaps this time they'll break the trend? After all, those other characters were created specifically for that first mission while Anderson is established. Plus in your first missions you're also accompanied by Kaiden, Jacob, Alistair, the 'other' Hawke sibling and Avaline. All of which can stay as squadmates for the rest of the game...more or less.
Perhaps the demo starts *after* the redshirt team mate gets killed?