Well ...
I mean, it's true that the only "real pirate threat" left in these modern times are pirates around Asia (although I _believe_ there are some occasional mostly-drug-related "pirate" incidents in the Caribbean as well). And modern day pirates are horrible -- unlike the Golden Age of Piracy, modern pirates have no small handful of people in their ranks who are merely after a freer way of life and are mostly not bloodthirsty killers who are happy to kill for profit (I'm not saying that there WEREN'T pirates in the Golden Age that were like that; I believe the 95% vast MAJORITY of pirates in the Golden Age were like that. But there were one or two who simply wanted a better life than what their world could offer them, and turned to piracy out of desperation.)
But ... I wouldn't worry about that affecting PotC 2 and 3 too much. There ie a _certain_ element of historical truth in the first PotC film (er, in that there were actually pirates in the Caribbean, and they weren't all very nice, and Port Royal and Tortuga did actually exist and so on) ... I imagine that it'll be about the same level of historical "accuracy," Asian pirates or no. I doubt that, if the Asian pirates turn out to NOT be on Jack's side, that they're portray them as being any meaner than Barbossa's crew in the first film (I would NOT want to meet anybody from Barbossa crew down a dark alley -- but still, we didn't actually _see_ them do anything really terrible).
I don't think we have to worry too much. I imagine PotC 2 and 3'll have the same fun as 1 -- I think the only reason for the Asian pirates is so that they can take our characters farther out into the seas than simply the Caribbean.
I will say, however, that I'll be disappointed if Ching Shih doesn't show up! ... ;-D