well, as much as i am a diehard playstation fan, even if it did come out on playstation (which it wont) i'd rather buy it for PC, because modding this game is half the fun (for me anyway) i've spent much more time modding TSL than i did playing it (same for K1). There are many reasons why this will be Xbox/PC exclusive:
1. Microsoft won't wont to give up any of that money to its competitors
2. The first two games were Xbox/PC, so unless they plan on releasing K1 and K2 for playstation or nintendo (like they did with GTA, first it was on the Playstation, then a year later there was the Xbox/PC releases) they wouldn't release the third in a series on a new platform, it wouldn't make any sense. Lots of playstation users probably don't follow xbox games (i know i don't) so most probably wouldn't have any idea what the story was unless they played the PC version, in which case they would probably buy the third for PC anyway
however, there NEEDS to be a SIMALTANIOUS PC and Xbox release! No more waiting Two extra months unless its going to have extra features like the yavin station in K1, but the features need to be better than that, since that was just a fancy shop which some pretty crystals and guns.