Well, first off, the PSH = Penguin rumor has been going since
2006, so I'm inclined to believe it's still just speculation.
Writer David Goyer said back in July that they are
leaning towards "new" bad guys for #3, so I wouldn't be surprised if they stick to that (though anything's possible).
But what purpose could the Penguin serve?
In the current Bat-comics, the Penguin is a mob boss... After Gotham's earthquake (don't ask
), The Penguin (with help from Luthor) started a black-market for goods in the ruined Gotham City. He used the cash he made to bankroll his new "semi-legit" nightclub/casino empire. He still dabbles in crime, but is played as more of a master-mind like Luthor, never getting his own hands dirty.
This version of the Penguin would work well in the movie mythos, as he could just be a quirky new mob boss who stepped in to fill the void created when the Joker killed off some of the Mob Bosses in TDK. Not really the main baddie, but probably a plot exposition device and or a thorn in Batman's side as he tries to do whatever it is he ends up doing in the movie...