Unless I've misinterpreted things nearly all of Namco's fighting game staff working on Smash 4 can only be a good thing, right? I don't care about the competitive side of things besides tripping but them being on board hopefully means the game balances the competitive side of things better and SSB4 avoids the ugly competitive vs. party gamers which was in full force during Brawl. Pac-Man also would be neat (though I still think one mascot per 3rd-party company is enough), though now a Namco rep is much more likely it'd be fun to see what ideas other people had.
The other thread discussing this news is beyond embarrassing.
Sakurai's games all have his distinctive style even when the teams are different: Air Ride with HAL, Meteos with Q, Brawl with Game Arts/Monolith/HAL etc, Uprising with Project Sora. They've all got that similar menu design, lots of unlockable content, various modes, and unique/deceptively simple gameplay. Namco can bring their tech and fighting game skills to the table, but SSB4 will still be Sakurai's baby. What is different in this case though, is that it seems like bigger names within Namco will be involved rather than just the main dev team.
So we'll see. I think we can expect a lot of Uprising's trappings like its weapon system and power-up grid (a basic version of which we saw in SSE) along with maybe a more, using Kobayashi's word, "powerful" fighting feel. They also know about creating large rosters- Tekken 6 has 60 characters- so maybe this is Sakurai's way of overcoming the difficulty of balancing a lot of characters. I know he specifically mentioned balancing as one thing he wanted to be able to delegate to his team. I'm not too familiar with how varied and well balanced Tekken rosters are, though. But before people get too optimistic about the roster size, remember, like Sakurai says, that there are 2 versions to make and more of a focus on changing the game mechanics.
Pac-Man is a good bet, yeah. Nightmare maybe for Soul Calibur? Kind of gruesome for Smash but at least he's more fantasy-esque. I can't think of any Tekken characters that stand out as good fits.
I think the most unfair assumption people are making is that just because Bamco is co-developing means that there will be Day-1 Paid DLC and stuff like that. Nintendo's corporate policy is pretty clearly against that, and they'll be the ones making decisions about matters like that. I don't think Sakurai is the type to be all that into the idea of paid DLC at all, but it's not impossible they do it for stuff like alt costumes, clones, and stages post-launch.