Like I said, you're comparing apples and oranges. There's precedent for third-parties having stages and ATs. Not individual items. This is something new. I'm not saying it's a bad thing for Pac-Man's chances (it's actually quite good), but it just doesn't auto-confirm him in my eyes since this is an entirely new phenomenon. If we had seen Ms. Pac-Man pop out of an Assist Trophy, then maybe I'd consider him instantly confirmed. But classic Namco games being referenced, as much as it helps Pac-Man, doesn't confirm him any more than Kremlings confirm K. Rool. Without a Mega Man or Sonic item to compare the S-Flag/Galaga ships to, we're left guessing as to what extent Namco's representation is going to be.
Didn't Sakurai specifically state that Namco wouldn't get special treatment just because they're working on the game? I was under the assumption that Pac-Man would be getting into the game on his own merits, in addition to Namco's involvement. Not because they're entitled to content because they're working on the game. I'd assume it'd be fair to predict that all third-parties will be given roughly equal representation, as in Brawl (which gave them each one character, one stage, one AT, music, trophies, stickers, etc). In Namco's case, having what appears to be their own version of the AT, without a Sega or Capcom equivalent, seems like special treatment, especially if they get a character on top of that. Now of course, there may very well be Sonic and Mega Man items in the game as well, which would make me a whole lot less suspicious. But at the moment, based on what we know, I can't bring myself to see Pac-Man as a lock. His chances have been boosted simply because we know that Namco is getting content in the game, but this doesn't confirm him by any means, much as I wish it would.
Not trying to be pessimistic. Just realistic. Some of us are convinced. Some aren't. What we should all be happy about, though, is that Pac-Man is at least going to show up for sure now, in some form.